There are 20-round and 32-round Colt factory mags, and of course, a ton of converted Uzi mags of various capacities.  I believe there are also some cut-down 10-round Colt mags as well.  As I'm sure you know, the Colt 9mm mag is based on the Uzi mag, but a channel was added to the rear spine to allow the follower to have a tab to trip the bolt stop.  Only factory Colt mags have this channel and tab.  I can see no reason why a LULA that is set up to work with a factory Colt mag would not work with a converted Uzi mag, and in fact, it may not even be necessary to design a separate Uzi loader.

-Troy

Oh, I should add that all that is done to convert an Uzi mag is to mill a mag catch slot on the side of the mag, and a notch at the top rear of the mag to allow the extended 9mm bolt stop to fit.

-Troy