I just bought a Ram Gizmo (unpopulated) for 5 pounds from 16/32 systems (http://catalog.zen.co.uk/actinic/1632Systems/16_32_Catalogue_Atari_91.html) . It can take 4 4MB SIMMs (30 pins) (of which i had plenty laying around), and it works like a charm.
I did hear some reports of people with problems running it accelerated when using 80 ns SIMMs, but so far i had no problems with my 60 ns memory.