I'd like to know how that works out for you? PM me when you get done, if you remember to?
I took a quick look at Enco's site and found they had stock on one reasonably priced jobber length (the short, stronger size) high speed drill set here
. That set includes #60-1 (0.040" through 0.228"), plus all the letter drill sizes and has a set of common fractional sizes in it, to boot. If you needed drills still smaller, I believe you can still get a #80-61 (0.0135" - 0.0390") set from Exacto, but those will probably all be too small. My thought is just to use the drills themselves as the hole gauges to find the existing gas port size and start at maybe 2/3 that diameter (half the area) and work up?