Good tip. I should be able to find a tube of the right diameter. Thanks Andy.

Mine perished so I ended up ordering the stock rubber blocks and will drill them.

Parts number are:

87210431A - Plug, RH
87210441A - Plug

They were about $15 AUD each. Expensive and could have been prevented with a bit of silicone spray once a year.

There is no part number for Ducati Performance ...