I bought a bunch of Black Aces for blasting and they cycle well. They are a bit long which may limit capacity. RIO works good as well and tends to be less expensive over the core American brands. Fetter as well, although I doubt we will see russian around much longer.
These are back - $100 now. Still the best price I have seen lately (although I have not looked much.)
https://botach.com/benelli-70052-m4-full-length-7rd-magazine-tubes/
Are you LEO or MIL? I tried ordering from CMC and was told no (as retired MIL.)
In the end, I ordered an M1014 with the collapsible stock then swapped the recoil tube from my regular M4. Much more practical then spending half the price of a new gun for just the stock.
I agree - I purchase most of my guns off the Internet as the local shops do not have the models I am looking for. I have a couple go-to FFLs to do the transfers. Osage County Guns is another source for Benelli shotguns.