Need battery door for vintage radio shack buggy special turbo
 

I have misplaced the battery door and can't afford to buy a parts car. Could i do a DIY one and what should I make it out of

ABS plastic sheet
 

I have the same problem for my Goodwill truck. I'm considering buying sheets of ABS plastic and cutting to shape. You can get the sheets in different thicknesses to suit your needs.

If you have access to CAD software, you could 3d print a solution.