To go with Joe's suggestions for synthetic western saddles, I love Bighorns. Out of the synthetic western saddles I've ridden in (I haven't ridden in all that many, just a Wintec, a Weaver, and a couple of Bighorns) I have definitely preferred the Bighorns. I've heard really good things about Abetta's as well.
I have a Kimberly (the "Synthetic Endurance" specifically, I didn't want an overgirth) from DownUnder and I absolutely adore it. I really can't say enough good things about it.
I have never, in my life, felt as secure as I do in that saddle. I feel crazy secure but then I can also hop Lacey over logs and post her trot without being confined. It's really wonderful. I'm actually finding myself getting over my fear of muddy conditions because the Kimberly holds me in so well that I really don't feel like I might fall (like I do in a western saddle and mud). I've found that it seems to really encourage me to ride better, more actively, and there's nothing about it that makes me ride worse.
I really cannot say enough great things.
Personally, I didn't find the DU people to be all that helpful but I never called, I just tried emailing. They certainly weren't rude or unhelpful, they just weren't excessively helpful.
I bought my saddle without contacting them at all (I just contacted them about saddle fit) and the saddle fits Lacey fine, so calling/emailing isn't entirely, 100%, necessary if you already pretty much know what saddle width and all you need.
Fabio - 13 year old Arabian/Lipizzaner gelding
Hazel - 14 year old Angora goat
Atticus - 4 year old LaMancha/Alpine cross goat
Rest peacefully, Lacey.