Not from the maker they supply a roll of tape to build up the ocular, which works fine.
I use shims from my Cobra/Wardy, you can buy the Cobra set but they're not cheap.

Time to "think outside the box" & go a bit "Blue Peter" maybe a section from a sink waste pipe fitting, gutter pipe, or plastic pot of some kind ?
Measure the gap, half it & that's the thickness you need.