I pick up bowsaws and bow bars whenever I find them cheap. I have no interest in running them and just redistribute them amongst the enthusiasts that enjoy having them. Some people around here think they're worth hundreds of dollars so they can keep those... I've rarely had one come my way on a running saw. Usually it's something that someone's daddy used to use and they're cleaning out... I've probably had 8 or 10 of them over the years. Maybe more, can't remember. Most are on Homelites, Poulans or McCullochs.
As far as adapting them to a different saw, it can probably be done. Often times the clutch cover will need to be butchered to make room for the bow. Saws with the OEM bow style clutch cover are nice to come across. And the guards are often missing as well. So bars with those intact have a greater appeal.