Commented: Eastern sources for mason beesFor Eastern bees I would highly recommend to contact "Our Native Bees" in McLean Virginia.
http://www.ournativebees.com/main/contact-us
Commented: Cedar Mason Bee House: okay to apply stain to it?At this time I would recommend a light water base stain for your cedar house or better yet to protect and beautify on a single application clear exterior water base varathane no odours and fast dry.