I have just picked up an official Wii Wheel from Toys R Us in Swindon. I had to ask in store, as there were not any on display. The entertainment dept manager went and collected a handful from the stock room for me.
Definately worth asking if you are going in - especially as they are only £6.99 - same price as Argos (now expired), and £1 less than the third party one that they also sell!
This item is not in their online store, you will need to ask instore (might be worth phoning before making a special trip - and make sure you speak to someone who actually knows what they are talking about!)