Woodcraft and routerbits.com both sell universal lucite bases for routers. You can get square or round, pre drilled or not. I use a square one for my handheld to do straight routs and clamp a piece of aluminum angle stock on both sides of the rout..it seems to work pretty good so far. I found that with only one guide and the round base, I would have a tendency to drift. Hope this helps you some. Good luck!
Ryan