I just had a look and it looks like, unless you are a commercial grower you can't buy it. There was a product containing it for use on sheep, but again I couldn't find anywhere to buy it so it's probably something only commercial farmers can purchase.
Mite treatments are extremely limited here. I had the best luck treating the coop with neem oil and spraying with fly spray in the coop every single day. They are tenacious little buggers. I do want to paint the inside of the coop but it's too wet and cold to do anything like that at the moment.
Doesn't look like we have that brand here but the active ingredient is the same as what is available here. We've just been astounded at how many mice were about. The hawks would cruise above the most open area of our property (far from the house) daily, swooping down to catch rodents. And we'd see mice around the house, even though there was nothing out there to eat! They nested in the walls of the aviary so DH drilled holes and filled them with expanding foam. They were in both our sheds, just looking for places to shelter for the winter I guess. It didn't help that we had a lot of long grass and weeds that our heifers were a bit little to eat through and stomp down.