Does it have to be wool? There are (IMHO) better alternatives now that are much cheaper.
Rambo has a heavyweight fleece option that is a thick plush quality. I’ve only needed to pull it out a few times, it is that heavy. Goes great under a rainsheet for the not-quite medium-weight days and does a good job of cooling my guy out. It is on par in terms of wicking capability as any wool sheet I’ve ever had and the bonus is I can wash it without fretting about dissolving it. Fleece also IME dries faster post-wicking, and doesn’t get the same smell that wool can if not air-dried properly.
I loved wool until I had to care for it. A lot of the horses at the barn I rode at in college had the old, oft-recalled-fondly wool rugs - they collect shavings and hay like no other, don’t breathe as well (IMHO) as polar fleece, were very heavy and you could not wash them… With fleece you can brush it down easily and throw it in the wash with no worries on ruining it.
Drawback to using fleece over wool is IME fleece tends to move around more under blankets, and also can stretch over time. Other drawback is I’ve shocked the everloving heck out of my horses with fleece and never had static be a problem with wool…
This is the Rambo one:
http://www.doversaddlery.com/rambo-g…ce/p/X1-24778/
I have it in the Newmarket version which appears to be discontinued. I got the 81. My guy is a big horse and he practically swims in the 81…
If you aren’t averse to two blankets I find the best drying out post sweaty-ride comes from an irish knit under a lightweight fleece cooler.
For wool sources, I honestly agree they don’t make them like they used to. They are outrageously expensive for thin blankets too. I think you’d be better off searching “wool rug” “newmarket rug” on consignment shop websites (or ebay). I haven’t been impressed with any of the wool coolers I’ve felt as of late.