I think I just used 'leather lunge' and then saved the search so it emailed me when one came up. I did have one altered at the saddlers so the chin strap fitted at the right angle / tightness. Sorry can't be of more help! I do sometime come across them in 2nd hand tack sections at tack shops too.
I got a great one on ebay was really nice i just searched leather cavesson and up it came is good quality and not expensive and works really well and you can attach a bit if you want to. good luck