As a buyer, you have much better protection to buy off of eBay. If the saddle is not as described you are protected through eBay and through PayPal.
But you do need to know exactly what you’re looking for unless there is a trial option. Are the panels the same as the one you tried? (If not it will fit your horse differently and affect your position as well.) If the saddle is listed by a tack shop they often offer a trial if you purchase through their website.
Another place to look for private sellers is Facebook Marketplace- High End Used Saddles and other groups. Again, you have to know what you’re looking for.
I’m also looking for a CWD right now- actually two, one for my mother and one for me (we’re nuts.) I think I just found mine. eBay led me to the tack shop, so I was able to get it on trial. CWD and Devoucoux also offer free shipping and returns on 30-day trials of used saddles. Equitack, which I think is the used saddle arm of Voltaire, and FrenchUsedSaddles.com, the used saddle arm of Antares, also have trial policies, though I think shipping is $50 outbound and your responsibility inbound with either of them.
Incidentally, my mother has been riding in my current saddle for the last year and a half, and it’s only recently that I’ve been able to talk her into getting one of her own. It doesn’t fit her at all. It was not until she sat in a saddle that fit her, on my horse, that she understood why she needed equipment that suited her. All of a sudden her leg was in proper alignment and she could use her position. It makes a huge difference, doesn’t it?