I can supply clear plastic ring types which are much better than the steel ones if that helps...
Ordered a couple of elements from Harvey for my Diana 35, 15.6mm diameter which are near impossible to find, received very quickly, fitted perfectly, have transformed my sight picture and allowed me to keep the rifle's original tunnel. I will be back for more sizes
Steyr LP10, Steyr LP5,
Vintage Collection - Walther LP53, HW77k Venom, BSF S20 Match, Original 35, ASI Target plus lots more