Amazon.com : M42-FD Lens Adapter, M42-FD M42 Screw Lens for Canon FD F-1 A-1 T60 FTB Film Camera Adapter, for Zeiss, for Pentax, for Praktica, for Mamiya, for Zenit : Electronics
Amazon.com : (2 Packs) M39 to M42 Adapter Ring, 39mm to 42mm Lens Adapter, for 42mm Focusing Helicoid : Camera Lens Caps : Electronics
M37-M42 Mount Adapter (KJAFDSXNR) by Ryo_MROpt
Asahi Pentax Takumar 83mm F/1.9 Lens for M37 Mount w/ M42 Adapter from Japan (C1749) | Big Fish J-Camera (Big Fish J-Shop)
M37-M42 M37 x 0.75 Female to 42mm x 1 Male Screw Camera Lens adapter - AliExpress Consumer Electronics