A search on Google throws up more choices than you can shake a stick at. Packaged, posted and delivered. But it is expensive and unless you know better, difficult to know when to press the buy button. Facebook is not much help either. Everyone has a suggestion to make and there is little consistecy in the recommendations that fly thick and fast.
Personally I prefer buying what I need at the local Farmers Market where the chances are that you will find a stall. Pre-packed stokkies are not a problem. The drier and more brittle the better. But I do prefer my biltong to be freshly sliced, moist and to come with more fat than is no dount, good for me.