Looking for an 18" dressage girth...............
Could swap for a 20" or pay
For some reason they are hard to come by - 16 and 20 are the most readily available!
I use the thorowgood cub saddle ones, but they are elasticated at one end (so don't like them for that). "Cub girth" is probably a good phrase!
Ebay have some for about a tenner (or used to)