I was in Poundland in North London, Wood Green and I came Across both a Wii Zapper and Wii Wheel for 1 pound Each. I brought One of Each. Its not officially by nintendo but I found the Wii Wheel to be really high quality. The Wii Zapper is very good too; It does its job. For a quid eatch you cant go wrong.
May be nation wide, not too sure. Its worth a look out if you live near or can access poundland to take a look
Note: Image may not be excactly like wii Zapper (3rd party Zapper) and the imagine doesnt include the wii wheel, but you can just google it