While a number of individuals have tried successfully to build their own zapper, it does require soldering skill and the ability to test the finished product. How do you know it is working?
ParaZapper offers a "shoebox zapper" already assembled and tested with several advanced features for only $49.00. This is about $10.00 more than Radio Shack parts and is of better quality. It is tested and calibrated.
Please remember, though, that this is a simple circuit board with copper paddles attached and does not have an outer protective case.