You get lots of newmarket 'style' rugs - they turn up around £20 ish on ebay. The proper ones are a fortune, though Horsewares effort is really quite good.
I had Shires wool newmarket exercise rugs for our ponies and though I think most Shires rugs are rubbish, these are actually beautifully made and really super heavy quality wool. And washable on a wool cycle! I got both second hand, don't know new prices, but would certainly get them again.