I don't have a thumbhole stock but I have an extra Hogue over-molded fiberglass & rubber stock if your interested in that.
I can't really find any decent pictures but suffice to say it pretty much looks like to OEM; maybe a shade larger. The biggest advantage is that it's the same rubber and pebbled texture they use on their pistol grips. Here'a a link with some pretty good info.
http://www.ruger-mini-14.com/hogueovermoldedstock.html
Price?