Yep, the .38 super, 9mm and especially the 9x21 will need a barrel swap.... hopefully a ramped barrel.
To the OP, you're better off just trying to find a cheap 9mm 1911. If there was such a product that would work well with 1911s, it would sell like hotcakes.
Thanks for the info. When I was thinking about 9mm slide I was really thinking about an entire upper w/barrel and all, but I'm guessing the .45 extractor would cause a problem. The .22lr upper kit can provide its own extractor and clear the one that is there for the .45, but a 9mm would be too close in size to the .45 and probably get in the way. (At least that's the way I'm picturing it now.) This would explain why I could not find such a beast.
Honestly, the more that I think about it the price difference between .45 and 9mm would probably not offset the purchase of a $250-350 kit anyway in the way that the price difference between .22 and .45 do. I have fun shooting my guns in both .45 and .22 and I guess that's what I'll keep doing....
Bryan