Cold Spring NY (1 hr drive)
Rhinebeck NY (2hours)
nw Connecticut and southern Bekshire towns
(Salisbury CT, Great Barrington MA, etc)(2+hours)

Princeton NJ (1+ hour)

None of thse are on the water, but they fit as small walkable towns with shops and restaurants

For a town closer to the water, I like Madison and Guilford CT.(2+ hours) Both are quite small though.

IMO, Saratoga Springs, NY is closest to P-town in terms of density of restaurants, shops, nightlife, even access to outdoor activities. Only it's not remotely on the ocean! 3 1/2 hours north of NYC, straight up I-87. It's most active from June to Labor Day, with the famed track being open for the last half of the summer; crowds reach their peak on the day of the Travers Cup.

What about Quogue, Southampton or Water Mill?

Ridgefield or New Canaan CT
Port Jefferson, L.I. - take the ferry from Bridgeport

Wow, great suggestions so far! I've been to some of them but
I'll check them out. Being on the water isn't important.

Also Brattleboro, VT, though a stretch at 5 hours driving time. Manchester, VT works too, though it's more about shopping (outlet stores) than the other stuff. It's also a good 4+ hours from NYC.

I'm surprised no one mentioned New Hope, PA, a lovely little town a few restaurants, quaint places to stay and some lovely shops.

I was going to suggest New Hope as well, with Lambertville next door.

"Not New Hope/Lambertville since I've spent a lot of time there also. "

Sorry. I obviously didn't read the OP.

The Hamptons including Sag Harbor. Fire Island is also a possibility.

Beacon, NY
Cooperstown, NY

Northhampton MA has a similar cultural vibe as Provincetown and fits all/most of the conditions.

Provincetown is unique; anything else is a poor 'second'. It's the cultural vibe (including that 'old Yankee' sensibility) and the seasonal excitement that make it buzz.
The 'big sky' against the blue and white seascape along with the glittering air make it a bit special too.

There are a lot of small walkable towns with galleries, good restaurants and a strong gay culture within a hour of NYC but there's really nothing like Provincetown.

If you're uptown, and you walk downtown, you could enjoy Chelsea within an hour.

The water is such a big part of what makes PTown itself!

I think I'd choose Cherry Grove, Fire Island or Hudson NY or Great Barrington, MA, just designated best small town in America by the Smithsonian. It is small but there are many other interesting towns in the Berkshires. Reservations may be already impossible for summer, at least on the weekend.
Brattleboro is on the list too but the shops are less interesting and less galleries, though a GREAT farmers market on Sat am.

There is no place like Provincetown

Thanks again for your suggestions. I now have a lot of research to do.
And, by the way, I agree that there is no place like Provincetown, but after 40 years of visiting I am just looking for an alternative.

City Island?

City Island is a good suggestion, too!

City Island??????

I wouldn't put it in the same category as some of these others, but yeah City Island is a great one-day (or part of one day) getaway while staying within the city limits! Seafood restaurants and shops, and I found the nautical museum fascinating: so much lore from the days of sailing power.

www.cityislandmuseum.org