I just added one to my Scotweb order...$12.99 each I recall...they come in three colors. Probably not the most cost effective or fastest method by any means since it's coming from across the pond...but since there were several items I was purchasing, it made sense to tack it on.

My plan for a brown one involves DIY using a dog leash, some brass hardware, and my leatherworking skills. You might also consider a stop to your local Agway, Tractor Supply Company, Central Tractor, etc....anyplace they sell tack for horses...you're likely to find a long leather strap with a buckle that could easily be converted.