Gaff Tape is used because is leaves little or no adhesive residue when removed. It can be purchased from many theatrical suppliers and can also be purchased on the internet. Here are some links to suppliers we have used in the past.
Bolts and Washers for the base plates are standard hardware available at any hardware store.
3/8" x 1" flat head bolt
3/8" fender washer
3/8" split lock washer.