What age are these ewes? If they are last year's lambs they don't need electronic tags, if I understand it all correctly. But not sure if you can still buy "old" tags.
I am using Shearwells, but have usually more than 10 tags. If you are starting from scratch (are these your first few to tag), then it may be cheaper to go for electropnic ones (and buy enough for any lambs to be born this spring), as you will probably have to buy a new tagger (or whatever they are called?) as well.