Buy one from advanced aquatics you can get what ever color or kind you want. He wont have them listed on his sight but if you call him he usually has pretty common ones for sale around 20 bucks or really fancy ones for around $100.
I would actually prefer a mantis that is smaller than a peacock. I had a G. ternatensis that I absolutely loved, but I lost him a year or so ago. I've been looking for another since.
As far as what I'd be willing to pay...it would depend on the species. I'm patient enoughto wait for one that is a good match for me. I'll check out the distributor you mentioned and see what he has available. Thanks.