I've also pondered on the 'SDRAM DIMMs are 64 bit wide' problem a bit.
Given the low price of the RAM, you can just use one half of it and forget about the rest (either double data or ignore it altogether). If you want large amounts of RAM, it's the easiest and cheapest solution - you could even use slightly defective modules. ;-)
Aiming at the 16 to 128 MB size range, it's surely easier and cheaper to use old PS/2s, they're free.