Based on this product's specifications, here are some alternatives and similar models
Massa adapter M42 to M39 threaded mount SB1703 — camera lens adapter
Summary description:
Mechanical lens adapter Massa SB1703 converts M42 threaded mount to M39 threaded mount, allowing attachment of M42 lenses to M39-bodied equipment. Metal construction ensures stable connection and accurate alignment. Useful for photographers and technicians who need compatibility between M42 lenses and M39 mounts for rangefinder cameras, microscopes or custom rigs.