Hi Fred,
I’ve bought decent eyepiece and finderscope caps on eBay. I’m not sure how big you need, but these sellers have 32-52mm diameter, and are cheap.
https://www.ebay.com.au/itm/New-Lens...GOVa0-neFQb9Ag
https://www.ebay.com.au/itm/New-Lens...GOVa0-neFQb9Ag