Adapting non-Dremel blades to Dremel Ultra Saw

[treesloth]

I have a Dremel Ultra Saw.  It appears to use an 11mm arbor to mount its blades.  That's an unusual size, which is problem #1.  Problem #2 is that there's a pretty limited range of Dremel blades available for it-- in short, wood, metal and ceramic cutters with very little variety in capabilities.  Are there any known-safe adapters to use other manufacturer's blades, such as those that mount to 5/8" arbors?  There are a couple of grinding/shaping discs that would be great to use.  Naturally, I would have to make sure whatever I use can handle the rotational speed of the tool.  Naturally, Dremel would like the idea of not being able to get blades from anyone else; hence the nonstandard size.