Arriving at Gare St. Lazare at about 11:AM and will leave from Gare de Lyon around 5PM. Is there a HOHO bus or some kind of tour I can pick up at Gare St. Lazare to kill some time and take my roll-aboard? (I assume the renovated Gare St. Lazare still does not have luggage storage?) Thanks.

You might think about taking Metro line 14 one stop from Gare St. Lazare to Madeleine where you can take a 90 minute Foxity bus tour.

http://www.foxity.com/en

Then, the same Metro line 14 goes to Gare de Lyon.

Maybe you can find luggage storage at Gare de Lyon? (Not sure, but I'd hate to drag all my stuff around with me - though it wouldn't be the first time!)

Having been to Paris before, I'd probably check out some of my favorite spots: the Eiffel Tower, Jardin du Luxembourg, etc. by Metro.

STore luggage at Gare de Lyon. Go for a walk on the Viaduct des ARtes, shop in the shops under it, and then come back and have a glass of wine in the lounge of Le Train Bleu before boarding your train. Envision what that would have been like at the turn of the last century when this was THE way of life!! Be sure to use the ladies' room (if appropriate--it is belle epoque also--except for the real plumbing!!)

As an alternative to a tour, you could explore the Bercy region/12th arrondissement around Gare de Lyon. If you have a lot of luggage then store it at the station first, here's a start:

http://www.nyceparis.com/what-to-see...ercy-area.html