You'll probably have to make one. Try to see if some electrical conduit works, from the local home center, or similar. Measure the inner and outer diameter before you go.
Forgot to add that plumbing adapters is another idea.
Edit...bah, just realized you needed one for the foreman. Fein makes an adapter that may work (available on Amazon), but I don't have a foreman, so I'm not sure.
I have yet to get around to making a custom one via a 3D printer (one I do I'll let you know)...I did find that you could use the festool round brush vacuum attachment that will attach to the Forman.
Edit...bah, just realized you needed one for the foreman. Fein makes an adapter that may work (available on Amazon), but I don't have a foreman, so I'm not sure.