When I changed out the 20 year old brake fluid in my 1994 Holiday Rambler I switched to DOT 5.1. Yes I had to order it, in fact the so called "parts professional" didn't even know what it was or that his store (O'Reilly) carried it. I had to look it up on their website and then give my PP the number so he could order it into the store for me. I guess there's not much call for hi-temperature brake fluid in the Texas flatlands.
BTW, driving my rig around the Rocky's, Sierra Nevada's, Cascade's and Olympic Mountains I'm sure glad I have it!
Some motorcycle dealers carry it (not Harley, Harley's use DOT 5) but you'll pay dearly for it at a motorcycle dealer.