You're going to like this :) 9mm carbine

[SKS Ray]

Or for some fun plinking! I have a Kel Tec Sub 2000 and have a blast with it.

I agree on the Sub 2000

 

[icyclefar]

Not a dedicated lower but this mag well adapter lets you use unmodified UZI mags in a Colt-type 9mm AR.

http://www.brownells.com/.aspx/pid=19669/Product/AR_15_M16_9mm_MAG_BLOCK_ADAPTER

Yup, that's the one I'm running.