The plastic washer isn't a particularly precision fit- - - -it's only there to keep the spring from rubbing on the shaft. There's plenty of squeeze in the spring, so the thickness isn't a critical measurement. As long as it slides into the hole in the housing and touches the shaft, you're good to go. It will wear into a good fit to the shaft eventually.
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!