Phil Tomlinson keeps a flock of registered Soay up on the north coast (of Scotland, not Lewis) and I know of someone near Aberdeen who has a small flock. Alistair Ferguson may have some on North Uist. I can't think of anyone on Lewis itself who has reg Soay, but Julie Suffolk the sec of the Soay Sheep Soc (advertises here) would be able to tell you of any new flocks.