MoonLite can machine a custom flange to fit your OTA if your particular refractor is not listed as a stock size above. Custom flanges up to 4" in size are $50 and 4" to 8" flanges are $100 with the purchase of a focuser.
We do the drawing and design, CNC programming / machining, polishing, and anodizing on site. It normally takes about 2 to 3 weeks to schedule custom work on the machines.