Mike,
It all depends on what you want to spend. Grainger's has some, but not cheap.
Im using some i got second hand that are from harbor freight, not the best quality by any means, but if you're careful they'll get the job done.
I would recommend using a battery operated drill as it'll run much slower than an electric plug-in one can.
And hold the drill with both hands to keep it steady, these tiny bits are easy to break, just looking at one wrong will weaken it, lol!
I've also got a very small set from Dremel, I believe that Ace Hardware sells some.
For sizes in-between the bit sizes, I'm using a jewelers file to enlarge the holes.
Something else that would work are torch tip cleaners, they're small , multiple sizes, and have a file-like surface that can ream out a hole depending on what you're doing.
I think you can get some of these at harbor freight as well.
Or you can search online for them.
Hope this is helpful.
Rick