He can either go for an A603, AmigaKit sells 'em, or go for the russian project of 8mb RAM, but these sollutions are for the A600.
Not for the A1200, if i was you my friend, i would skip the RAM expansion for the 1200 and i would go directly for some cheap 030 with RAM. I have to say a RAM expansion would double your A1200 stock speed, however, to double the speed of something that crawls it's not much. Go for a x4 speed or more. That means a 020 28mhz, or a 030 25mhz. That's my advice.