Take a look at:

http://www.srbfilm.co.uk/

I got exactly that adapter from them and use it regularly on my minolta MD mount body. SRB film services (UK based) supply just about every adapter you could ever want. The only drawback is that if the M42 lens is automatic i.e. you cannot stop it down manually then you can only use it at full aperture.

I bought it some years ago but it was not that expensive I recall.



Les