The first tan breeches in my photobucket sold (the flared leg ones) - have a pair of vintage western ones (use for showmanship or show). Those are approx a size 8/10.
I do have 3 used sz 28 (approx a ladies sz 8 - medium) tan or khaki coming in next week - they'd be $ 15-20 each.
On a general note on breeches fitting - most go by waist size & do stretch some. For me I'm usually a sz 12 so most of my breeches are a sz 32 (altho technically my waist is about 34...)
Hope that helps!