Hi L154 I was in the same boat earlier this year. [I have got my Stubben Siegfried 29 jump saddle] and was after a dressage saddle too. I got one off eBay an Avalon size 30 which didnt fit
so I resold it and didnt lose any money
.
One thing I would say is that the different styles the Siegfried, Scandica have different trees and therefore a 29 in one that might fit might not necessarily fit with another!
Just wanted to share really, dont want to put you off, you might get lucky
Dont get a stubben dressage saddle without trying it, as the stirrup bar is quite far forward and makes it difficult to keep leg in correct position....
U could always get a stubben specialist to come out (it will cost though) and you could try the saddles, get to know what suits you and your horse and then buy one second hand. or does a local saddlery let u take out second hand ones on approval so you can try them?