The Russians probably aren't even sure what all they used in their Muff pedals. "But Commissar, it is hard to work with mismatched parts and big boxes!" "HA! In Russia, pedals build you!" But if you want modern analogs...
- Stomp Under Foot makes a whole selection of pedals based on the various Muffs. Their Green Russian is a Bubble Font clone; the Ram's Head and Civil War (which you can get as a dual unit) follow those versions of the Muff. Those are just the ones I know about off the top of my head.
- Wren & Cuff makes their Tall Font Russian, which is exactly what it sounds like: a Tall Font clone. I personally don't like the mismatched knobs (Muffs always had three identical knobs) but that's a minor beef.
- Black Russian Muffs are still commonly available for reasonable prices on Reverb. If you want a modern version, I am told that the EHX Bass Big Muff is based on the Black Russian. I owned a BBM for a while and wasn't blown away by it, but YMMV.