For a transport service, I would recommend you contact Park Lane, see See http://www.hongkonglimo.com/. They can arrange for hotel transport and can also take you to Shenzhen. I believe their rates are posted on the website or you can send them an e-mail. As noted above, most any hotel can provide airport transport service and car service to Shenzhen.

You do not need, and really do not want, a driver for sightseeing in Hong Kong. The Central and Kowloon areas are quite compact and easy to see on foot. The major tourist sites do not lend themselves to being seen via a car (the Star Ferry, Kowloon Esplanade, Peak Tram, mid-levels escalator, outlying islands like Lamma, Cheung Chau), many tourist areas are closed to cars entirely or access is restricted to residents (much of Victoria Peak, many street markets, virtually all of Lantau and most country parks). If you use a car to take you from site to site, you will spend a lot of time in traffic and then calling your driver after he has gone some where else to find parking. There is virtually no on-street parking, so your driver will be hunting around for garages.

I assume you already have your multiple entry visa for the PRC. Also note that Saturday December 25 and Sunday December 26 are public holidays in Hong Kong, and you may find the border areas to be quite congested with people traveling to the PRC for the holiday. Most schools are closed for 2 weeks starting December 20 so again, immigration lines at the border could be long during this time. It is possible that some stalls and shops in Shenzhen may be closed on those days as well; although this will be more the exception than the rule.

If the purpose of the trip is to shop for at least 3 out of your 5 days in Shenzhen, then I would suggest you consider staying at the really wonderful Ritz-Carlton Shenzhen. Besides being an excellent hotel, this will save you at least 2-3 hours a day in driving between Hong Kong and Shenzhen. You can take a ferry directly from the Hong Kong airport to Shenzhen (by passing Hong Kong Immigration entirely), or arrange for a car service to take you there (which means going through Immigration twice).

You may need or want to hire a personal shopper, as IMO drivers are unlikely to be able to provide the detailed information you need. I would start with your hotel concierge who may have suggestions. You might try something like Asian Cajun at http://www.asiancajun.com/shopping.htm or even just get a copy of Suzy Gersham's Born to Shop, Hong Kong, which includes a section on Shenzhen and might be helpful. Otherwise, and even with the help of a profession, I doubt that you will find “very good replica” jewelry, or “very, very good replica” handbags in Shenzhen. You will find a lot of poor quality fakes. I have lived here a long time and gave up on Shenzhen as a “good” place to shop some time ago. If you want fakes, I would go to Canal Street in NYC and not fly thousands of miles to buy them in China.

If you want designer handbags, consider purchasing second hand versions at Milan Station shops, which are all over Hong Kong, see http://www.milanstation.com.hk/. You can also have some replica bags made here, such as a Birkin or a Kelley bag, where the style would be copied but not a trademarked leather like Louis Vuitton or Gucci. While not cheap (starting at US$300 or so), they are a fraction of the cost of the authentic item. But the quality is far better than you would get with a fake.

If you are a retailer of these items, you may want to establish a relationship with a wholesaler either in Hong Kong or the PRC (although I don’t believe the law of most countries will allow you to legally import fake merchandise which involves a trademark). As a start, you might contact the US Commercial Service, which is a department of each US embassy/ consulate. While their primary task is to promote US business abroad, they do provide advice on doing business in each country. Take a look at http://www.buyusa.gov/hongkong/en/. The US Commercial Services Dept for China has a website which might also be helpful, see at http://www.buyusa.gov/china/en. If you are not a US citizen, most other counties have a commercial service section in the embassies/consulates, consult websites.

If you are just shopping for yourself, also bear in mind that while US Customs may allow you to bring back 1 item which is a copy of a trademarked good, the rules do not allow you bring in multiple items. See the US Customs and Border Protection website at http://www.cbp.gov/xp/cgov/travel/vacation/kbyg/prohibited_restricted.xml#TrademarkedandCopyrightedArticles. If you are not returning with the goods to the US, many other countries have similar laws which may affect your ability to bring in counterfeit trademarked items.