The Moskva may be modified - the lens/Shutter assembly is held in place with a screw-on ring on the inside of the bellows. But usually people try to get a slight wide-angle effect with pinhole cameras, and here the bellows will interfere.

And IMHO it would be a shame to salvaga a SuperIkonta-cousin for something like this - the Moskvas are up to good results with their Tessar-derived Industar lenses.

If you were in Europe, I´d recommend a Agfa Clack (sold as "Weekender" in the US by Ansco, but probably quite rare over there!). The Clack is cheap in Germany - 1 to 5Euro on Ebay and flea markets.

It is simple to modify her, just pry off the cover, remove a single screw and the lens comes off and you still could use the shutter to time the exposure.

See for details.

I made a insert mask to allow usage of 35mm film with the curved back - quite cute effect. :-)