There's a chap on Lewis goes to one of the tup sales in Lairg every year; we met up with him at a B&B there in early October two-and-a-half years ago. I can't remember if he was buying or selling sheep but he had his trailer there.
A long shot, I know, but if you could track him down....
And I don't know about Shetland but the cattle ferries they use to transport cattle and sheep from Orkney are so well equipped that it doesn't count as travelling time! Every bovine has its own stable, bedded, with hay and water - so it counts as rest, feed & water time and they are ready to be carted on the road on arrival at Aberdeen.
If you do decide to bring livestock up from south of the border, please give some thought as to any health checks that may be prudent - Schmallenberg, TB, etc. It would be awful to unwittingly infect the island with anything
