I found a company that sells rubber feet!

Correct Vibroplex size but Super Soft (to see if that helps them stay put!)

They're a 0.25 inches high and nominal 0.671 diameter.

Small Super Soft Round Rubber Feet - 0.250 H x 0.671 D
https://rubberfeet.us/store/?model_number=SF6T-TPR64

The next height up if but also about a half inch wider in case you want you bug higher.

Standard Super Soft Round Rubber Feet - 0.437 H x .1.062 D
https://rubberfeet.us/store/?model_number=SF10T-TPR64

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