Not sure if a contact in Australia is going to be of any use to you,
but I'll mention it anyway.
There's a business called Ultissimo Products, who specialise in pure
mohair products for horses. They can make any girth up to your
personal requirements. The girths are extremely strong and hard-wearing,
and are also ideal for sensitive horses who have galled easily in the
past with other girths. They would probably be able to put in elastic
for you, or more likely plait up the fibre so that it has natural
I have a couple of sets of their mohair reins - I personally
prefer them with a bit of natural elasticity, but they can also plait
the reins in such a way that removes the elasticity altogether.
Anyway you can check out their web page on
and their email address is email@example.com