Not quite sure what you're after but you can get a Voyage 200 graphing calculator for not much more than a RasPi now - it's got a Motorola 68000, a qwerty keybo

Not quite sure what you're after but you can get a Voyage 200 graphing calculator for not much more than a RasPi now - it's got a Motorola 68000, a qwerty keyboard, a sunlight-readable screen, a serial jack, a useful OS with many games, a C IDE, a disassembler (both onboard!)... and it runs on 4 alkaline batteries.