my realistic ones are from PSX but, I am thinking they are pretty much too much money anymore on ebay so, I am still thinking about this...
I know they have to be out there.
I would do a wild guess that maybe maybe serendipity could have one since I know I have a horse from them and a goat that is very beautifully done realistic but, I have not looked to see if they have sheep...
most of my sheep lean towards the cartoonish side.