the two small ones a Compur & a Prontor have mint Novar lens cells fitted.
Does the Prontor look as if the threads are 22.5mm? The Prontor SV on my Ansco looks like it would do but I'm not going to take it apart. Just holding the SA rear element up to the back of the Prontor, it does look like it would fit. I can't tell from the front as it has the scale focusing ring on it.
I am going to look for a cheap Isolette or something similar with bad bellows so I don't mind taking it apart.