I've been looking around and that's about as cheap as you're going to get it probably. Considering the original price is £19.99, that isn't too bad...although I'm waiting to see if Virgin puts them up on the website, because their prices are usually the cheapest (for Wii games anyway). I don't think Play has listed a proper price yet either.
Edit: There is this on Amazon which seems almost identical to the Zapper, apart from slight differences on the front handle.
