300mm F6.3 Catadioptric Compact Telephoto for Mirrorless Cameras – Samyang US
Rent Samyang 500mm f/8.0 Mirror Lens with 2x converter & filters in London (rent for £12.00 / day, £8.57 / week)
Opteka 500mm/1000mm f6.3 Telephoto Mirror Lens for Canon EF EOS DSLR Cameras 388800142848 | eBay
500mm F/6.3 Mf Telephoto Mirror Lens +2x Teleconverter =1000mm For Nikon Canon Sony Dslr Camera And Macro 4/3 Mirroreless Camera - Camera Lenses - AliExpress
Amazon.com : Opteka 500mm f/6.3 (with 2X- 1000mm) Telephoto Mirror Lens for Canon M100, M10, M6, M5, M3, M2 and EOS-M Mirrorless Digital Cameras : Electronics