Fergus,
I got mine at Laacke & Joy in Brookfield try a google search Dogfunk may carry them or EVO not really sure if the big box chains carry them but worth the look. Laacke & Joy's does have a web site not sure if they are on there though. I've used these since the 80's on tow ropes.
If you ever make it up to Alpine Valley which is currently making snow to open next weekend drop me a line love riding with guys from the forum. Made some good friends off here from the Chitown area.
EDIT:
2 pairs are still in wrappers I bought as just in case equipment.
Maker is Kombi "the glove protector"
Eriks bike shop national chain
Summit On-Line
Tow rope glove protectors