I actually got them as I recall a couple of years ago, in conjunction wit the passage of the Washington magazine capacity limitation law; I got them as a pro-active measure as the bill(s) started to meander their way through the Washington legislative houses. I obtained them through my FFL at the time commercially, the left side of the tubes is rollmarked "PB CAL.9PARA-MADE IN U.S.A. ACKK., MD" so perhaps Beretta USA changed over to providing the 92S cut-outs on later production 10 rounders-or did so in conjunction with their move to the Tennessee factory.
Disassembly is easy with these magazines, so clean-outs for maintenance shouldn't be too onerous if you can't get the ones without the cut-outs, but you might want to call BUSA and see if they have any NOS without the cut-outs still available.
Alternatively, it might be worthwhile to check with MecGar, which are well regarded, but I don't have any experience with their 92 magazines personally.
Best, Jon