50mm lens holder for cheap eBay 20D lenses

Since I am a Internist rather than ophthalmologist I can't justify a $500 Volk 20D lens, so I purchased a $50 lens off eBay from India (link below) which works great but is a smaller diameter by a few mm than the one that this older is designed for. So I created my own in OnShape CAD and here is the STL and STEP files for anyone who wants to use the cheaper lenses.

https://www.ebay.com/itm/20D-Double-Aspheric-20D-Ophthalmic-Diagnostic-Lens-Top-Quality-FREE-SHIPPING/192337418918?ssPageName=STR