I've a Bailey and I use 18 through 10's. The smaller needles aren't recommended but as long as you have good tension and move slowly they work. I only use smaller than 16 when the project demands it. I buy most of my needles at Joanns . Usually Schmetz brand. As long as they have the one flat side, any brand will work. Its basically a domestic machine with wheels and a frame, so most standard needles work. Do you belong to any of the Bailey Forums? Theres one on yahoo groups and one here
http://bhqbaileyhomequilter.proboards.com/. You'll get more answers alot quicker on one of those. The yahoo group has more activity than the proboards. Proboards was started to replace the one on yahoo, but the older gals don't like change so both are up and running.