Apparently they have them at both Primark and Matalan - you might be lucky. I have also seen them in my local Tesco. Could not tell you cost though.
My MIL bought a pair from Primark in Portsmouth yesterday for my DS, as he is only 2.7 but completely obsessed by Dr Who and Daleks. How, I do not know, because as far as I am aware he has never seen Dr Who, but I think it is via the CMs older daughter.