Have you been to llanybydder sales today (last thursday of every month if you've missed it)? Theres normally something there, i sold a 15" saddle there a few years ago.
damn it I have a 16" I'm desperatly trying to pawn off on someone! It was given to me and is now just gathering dust, if anyone wants it for P&P let me know! V
Keep looking, I do have a old but neat English half panel 13" in brown for sale - where are you?
Sadly, my bargain of the century English 14" Extra Wide show hunter saddle with point straps is not - but I did get it from Ebay last year.
Also try Saddles Direct, she sometimes has pony saddles