Moog Rogues and sh101 - both cool and can still be had for a moderate price.... starting to get collectable though
As for transistor organs - more like the old gibson organs or vox continental - on the cheap end a Gem wizard. Awesome beast when used with RAT pedals..
Can't be arsed to get the bass out? Me thinks you're looking for something cool and monophonic - so an sh101 might be cool.