If you want to make your saddle work, a sheepskin for your seat and comfortable stirrups might just do the trick. BTW, nothing looks awkward in endurance, everything goes in mix'n match of riding tack/styles, as long as you and your horse are happy.
I use an AP arabian saddle company saddle. I added Cashel stirrup cushions (see pictures) and use a Toklat woolback pad. My mare hates synthetic pads. I've added D-rings to the saddle and voilą!
Saddle shopping is a whole different game. You can certainly find a deal (go on FB endurance tack swap page), you'll see tons of saddles for sale. Finding the right one can be a headache. I'd say, you'd better start with what you have and look and try other saddles at rides to see what fits you and your horse best.
Some treeless are both good quality and affordable. Barefoot Cheyenne Drytex comes to mind. You need an excellent (read: expensive) pad to protect your horse's back though. Wintec can also be a good choice. Aussie are often as heavy as western.
That's my saddle, you can see the stirrup cushions.