eBay is full of those:

http://shop.ebay.com/?_nkw=%22micro+drill%22+carbide

or similar tiny carbide end mills.

My question is how usable are they on a hobby sized CNC machine like
my Bridgeport Interact, with slow top speed. Is using them totally out
of question, or just frustrating, or perhaps they are handly for small
work?

i