Most commissioners don't specialize in one style of clothing like that, unless it's historical. The kinds of commissioners you find around here are jacks-of-all-trades, which can be both good and bad.
Unless you're looking for strict historical accuracy and need to go to someone with period historical experience, your best bet is to keep asking your potential commissioners about their experience with uniform sewing. Experience does matter, I know - especially if you need your uniform properly fitted and tailored, correctly seamed, and authentically lined with the right kinds of pocket and welt construction techniques. But outside of historical accuracy, you just need a commissioner with overall experience - technical experience and proficiency. It can be hard to find, but we're out here, floating along.
On the other hand, if you DO need historical accuracy, I suggest looking for specialists in period clothing. That would at least get you pointed in the right direction, even though techniques vary massively between someone who's an expert in Elizabethan versus Victorian, for example.
Founder and President, Madison Area Costuming Society, a chapter of the International Costumer's Guild
Strange Land Costuming - www.strangelandcostumes.com
Director, SF&F Masquerade
- COSTUMECON34 - Madison, Wisconsin - May 6-9, 2016 - www.costumecon34.com