Heck industries makes some nice hand held millers that bevel. I have never used one, but worked for a structural shop that needed them badly once. They were welding, or attempting to weld, 5/8" angle - vertical down. The CWI claimed full pen capability in one pass for his 'weld procedure'. I cut several up, and they of course had virtually no pen. The solution was to reject all the structures coming through the shop, and rework them by beveling with a hand torch and then rewelding to full pen in several passes. It would have been a snap with a Heck hand beveler.
http://www.southern-tool.com/store/HeckBevel-MillAndPlateBevelers.html