There are hundreds of 5/16" OD springs on Ebay. Measure the diameter of the coil wire, pick one that's close, and cut it to length. "It ain't rocket surgery, ya know!"
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!