just about any vest for m4 magazines is good for mp5 mags. i personally prefer ones meant for one mag per pouch (such as an eagle vest, or single m16 mag molle pouches) because once one of the mags is removed, the other still sits in there pretty well. there are plenty of smg pouches as well. just check out
www.optactical.com
surprisingly my favorite mp5 setup is actually my nam gear. the triple m16 pouches (alice) i have on it have these dividing strips and hold 6 mp5 mags very well, you can't close the top, but you can wrap it over the top of the mags, holding them securely.