Go on line to gunpartscorp.com, and look under Bryco. There are some parts there.
To be honest with you, these were low dollar guns of indifferent quality when new. The company is gone, and parts will eventually be a problem.
Rather than puitting additional money in the gun, I would be tempted to wait for one of those "feel good" gun buyback programs, get what I could, and start saving for a better quality gun. Or, if there is a sentimental value, pull the firing pin out to make the gun inoperative, and put the gun in a shadow box.
And where ARE my manners? First time poster- welcome to the forum. When you get a minute, stop by the intro thread and say hello.