Jonathan Holmes has released Midnight Wild for the LDK Game and Bittboy, might be a good fit for the RS-90 given it was originally an Arduboy game and has tiny resolution requirements. Source is on his site here:http://crait.net
GPD Win, GPD XD 64gb, Pap KIII-Plus, RS-97, RS-90, New Bittboy, 3DS XL, DSi XL, GBA SP, GBBC Clone, Gameboy Pocket, PSP Go
HP Envy M6, Toshiba Click Mini 8.9, Acer 522, Dell Mini 9, HP 2133
Psion 5 & 5MX
Tons of other old laptops and tablets.....