I think there are very few if any stores in MA that will carry ADA now.
After ADG gave up on ADA a couple years back, ADANA has a continued monopoly on the supply for ADA stuff now. It's pretty hard for an east coast store to be competitive because of shipping costs etc. It's often more financially sound for both the store and the consumer to buy it from ADANA directly. I believe ADG cut ties with ADA(NA) because they couldn't provide reasonable prices given the prices ADA(NA) was giving them. It's the same reason why I dropped ADA. I didn't think it made any sense for me to bring in ADA stuff, then sell it for the same price as ADANA, only to lose money. I'd have to raise prices just to break even, and since that's not fair to the customer, you might as well send the customer directly to ADANA right? Stuff like this is probably why an ADA-focused store shut down a few years back (I think it was in the NJ/NY area?)
That said, a few alternatives have come on to the scene to compete with ADA products, namely Mr Aqua stuff. However, even Mr. Aqua stuff is hard to sell competitively on the east coast because of shipping costs from CA. At least it's more reasonably priced.
I have ADA 60P + 602 AquaSky/anthracite cabinet and instead of ADA aquasoil I put mr aqua shrimp sand. From my personal testing, mr aqua shrimp sand leaches less into the water and provides for a more sterile/stable/predictable setup, while retaining its structure very well. I've had the shrimp sand in a tank for 2+ years, then after breaking down the tank, the granules were still intact. There are also people that swear by ADA aquasoil and that's cool too. That's why I sold ADA aquasoil in the past. In my mind success depends on the user's ability to understand what they're working with and what they prefer. That's why some people can thrive with miracle gro and stuff like that or local garden soil. It's because they know what they're working with and are making it work.
I'm not sure if Han has an actual store, in that he has a sales/use tax id or if he imports stuff and just resells off the books. I think "lighter weight" operations are a good way to meet growing specific demands because it's really nuts for any "retail" store to be able to carry everything someone would look for. I'd rather have more diverse options! I look down at stores that try to squash hobbyist operations. Extreme enthusiasts are what keep this hobby growing, sharing their passions with others whether it's for profit or simply enjoyment. When all a store cares about is profit margins, that's when newcomers to the hobby lose, burnt out by what they believed to be a trustworthy source. I've met Han before and I think he's a super nice and great guy. He knows what he's doing and is willing to teach others. That's all I would look for when buying from anyone.
I'm not trying to plug any brand over one another here but just trying to explain how I see ADA availability and why things are the way they are. I have bags of mr aqua shrimp sand and mr aqua black aqua soil if you're interested, located in Natick.