Did you check airrifleheadquarters.com or vortekproducts.com?
...Thanks. Airrifleheadquarters didn't seem to have anything, but Vortek looks good. Ill just have to do some math to get the right size spring.
You will need either the outer diameter of the existing spring coil or the inner diameter of the piston. Remember, the spring coil must fit inside it. The diameter of the wire used to wind the spring is helpful as well. An exact match is not necessary but you should stay close. You'll also want the number of coils. If you measure the depth of the piston and divide that by the spring diameter that will give an absolute maximum number of coils possible. Go for about ninety percent of that number.