Try Newark market for commercial ewes. If you haven't kept them before though I would suggest that you don't go for maiden ewes and look for ones that have lambed before. I am moving on to badgerfaces as they seem quick to mature when mixed with the right tup. This year I have had really good results with ryeland x easycare.
If you get stuck pm and i will give you the details of my neighbours who keep commercial sheep.
Regards
Rosey