There is already a link here in the forums to a very good replacement from a replica radio store (in Holland methinks?). But as a cheap alternative and if you ain't too picky (and you can live with brown) you might consider using vintage style Danelectro knobs??
They might serve you OK as an interim: KNOBS
"A little song. A little dance. A little seltzer down your pants." -Chuckles the Clown
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