There are several recipes for oatcakes on the net, but you can order the Staffordshire mix - and variations on the mix, plus other products - from:

Oatcake Kitchen

It's actually a little street corner café and takeaway in a part of Stoke called Dresden, and it does a roaring trade. People come for their filled oatcake orders and carry away huge boxes and bags for lunch. Good, prompt service over the net too - I've tried it.