So, being an inventive jackass of all trades, I went ahead and found out how to go about making one on my own, and it turned out to be pretty damn cheap!
This is my first DIY Instructable, so I apologize in advance if it seems as though I have no idea what I'm doing, simply because I may not. However, I digress. Onto supplies.
Materials you'll need:
-a potato masher like the one in the picture
-Dremel with metal cutting blades or a hacksaw
-red (not sure of the strength rating) physical therapy band, or one thinner and stronger (yes I know the band in my picture isn't red, I started with a weaker band that performed like crap)
-piece of strong, supple leather about 2" x 3"
-zipties or wire with a strong breaking point
-knife or scissors
-either a chainsaw sharpening dremel bit, or steel files
Step 1: From masher to slingshot fork with 2 cuts
It is crucial to the longevity of your sling bands that you round off your cuts as smooth as possible, with no barbs left over that could later cut into your sling bands as you draw them back and put tension on them.