Jason, you appear to be at the rough edge of pen makers size convention. That is the nominal size thrown around is the bit diameter commonly specified, which has passing relarionship to the tube outside diameter, let alone the tube inner diameter.
So if you have a candidate tube, it is calipers and the tube/bushing tables.
There are tubes that slide into other tubes, making adapter bushings, etc.
So think and communicate like a machinist to get a really detailed discussion going.
(I don't think I have used a 9 mm drill bit for drilling blanks)