Scaleable replacement camera lens cap. 

unlock xyz scaling and scale based on percentage of the required size on the x-y planes only. keep z on 100%

eg. you want a 77mm cap. from 82mm thats a difference of 6.09% so scale the x-y to 93.91% and print.

i have confirmed this works for sizes 52,55,67,77,82,87mm and all worked fine.