First of all, it's totally understandable that horse can be out of the price range. Nothing wrong with it, you'll just have to keep looking. Second, I do know trainers who'd help or recommend the horse without making a commission (if you have good long-time relations with the trainer). But of course it's not always a case.
OP, I think you have to be more active yourself looking for the horse and trying different ones. When you find one you really like and can afford then it can be time to talk to the trainer asking if she could spend some time to go with you and evaluate the horse (and offer to pay the trainer for the time, of course).
As for the rescues, they do have good horses, but I've never seen a horse with any serious training coming from the rescue. W/T/C/small jumping is pretty much a basic thing, doesn't mean horse will be good at jumping or dressage.
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."