As you will see, the instructions at this link are fairly thorough. They describe making a "variable frequency generator", which is just another way of saying a zapper that can be run on several frequencies, with parts list, and schematic, to include the all-familiar 555 circuit that the Hulda Clark zapper was originally based on. Depending on how well you shop, the parts will cost you around $25 to $40, but this IS a solder-based design. Have fun and good luck.