Try Fall River Army Navy Surplus on 228 South Main St in Fall River, MA.  Phone number  (508) 674-2002  A few blocks uphill/south from City Hall.  Bring a small flashlight to investigate the display cases, as they are not lit.  I've been to the two above, and FRANS is better, IMHO.  Bayonet prices are wildly expensive, though.

The store is a jumble, and crammed full of stuff, so it will take you quite a while to search the place; put a few quarters into the parking meter, and note the time allowed.  If you're looking for something specific, ask Mr, Han, and he will show you where it is, if he has it.  Don't ask for things that are illegal in MA, like magazines and two-edged blades (daggers).

Mr. Han is pretty sharp, for an elderly gentleman, so be polite, introduce yourself, and ask him if he has what you are looking for.  If not, then ask him if you can look around.  He understands the difference between "GI" and "NOT GI" perfectly well, and if asked, will be frank with you.  Fall River being somewhat sketchy, he is always on the outlook for shoplifters, so be up-front, and polite,  If you are reasonably well groomed, well-dressed, and don't give off a drug addict /shoplifter vibe, then it's all good and you will not have any problems.  Mr. Han is sort of a friend of mine, we having dealt with each other for many years, so possibly I am being a little protective of him.  He is a professional merchant, but a good man.

As always, Cash is King.  After laying out your purchase, ask the owner, Mr. Han, how much he wants, Cash money.  Sometimes he'll knock of some money.  Tell him you heard about his store on AR15.com.  I'll mention to him that the word is out here.

Not too much brand-new, top-tier stuff, but I don't think the average Arfcommer will be disappointed.  I have found some damn good bargains there, like LBT, TT, and a lot of other top-tier stuff, but such bargains are hit-or-miss.

Also, there's Uncle Sam's Army and Navy Surplus on 548 Kingstown Road in Wakefield, RI. 401 782 2565.  More civvy stuff/repros that FRANS, but some bargains can be had.

As is often the case, frequent trips to a store will allow you the first to find a bargain.  Lots of GIs turn-in gear for cash, and if you're there to find it before the next guy, it's your bargain and not theirs.  Going to the store frequently allows you to be the guy that spots the bargain.

There's a store, actually two locations with slightly different inventories in Mystic, CT.  Might want to check them out as well.

John's Surplus, 1800 Airport Road, Warwick, RI 401  738 8735.
Decent selection of clothing and other field gear.  Clothing is well-organized, and plenty of turn-ins in various sizes.  Mostly milsurp, with repros creeping in.  OTOH, occasional gear from returning units, based nearby, which might be occasionally available, and frequent visits will make such occasional stuff available.

Prices are high generally, and little room for dickering.  Investigate the contents of the display cases carefully; some items of interest there.   There are a few bargains concerning the older surplus stuff that he has not bothered to re-price.  I've been a customer there for years.  I'd give the store a weak thumb's up.  Many of RI's larger gun stores are within easy driving distance, so that's an advantage.

Nowadays, I don't go there much, but if in the area, will do so.

There's an Army/Navy surplus store in Newport, RI; 111 Swinburne Row  Newport, RI 02840, but I have not been there in a long time, even though it is nearby.

Given the store's location, with high rent, I wouldn't expect any bargains, not to say such bargains escape the owner's notice, as is often the case.  If in the area, investigate.