Remedies for knobs on different shaft sizes?

Most pots, and some knobs, are available with more than one shaft size so it may be easier in future to buy the right ones. However, a retailer might only stock a few (possibly one!) of the manufacturer's combinations so you might have to look around to find what you need.

BTW are you sure it is 5.5mm - I thought 6mm was the usual metric size.
 
Most pots, and some knobs, are available with more than one shaft size so it may be easier in future to buy the right ones. However, a retailer might only stock a few (possibly one!) of the manufacturer's combinations so you might have to look around to find what you need.

BTW are you sure it is 5.5mm - I thought 6mm was the usual metric size.

I bought some mini ones of ebay but I needed to pair them another value that was unavailable from the same supplier hence probably having to use two different shaft sizes.

Looks like a bit of tinkering may be in order?