Hi rawk crawler. ebay might have a controller. you can also try looking around at yard sales.
the hardest part about installing hobby grade electronics in toy rc's is the steering. your going to need to make a servo fit where the toy grade steering servo is. they are not wired the same so it won't work with hobby grade. the rest of the hobby grade electronics install isn't so difficult. so if your up for some modifying, tinkering and building it can be done.