USB controlled mains switch

I'm looking for a USB controlled mains switch (230V AC) that I can connect to a PI to turn a mains power supply on and off.
I've done a bit of digging around on the net, and the options seem to fall into two categories, either a relay device which means having to rewire the device (which I'd rather avoid), priced around 30Euros or one that sits in line (between the device and the supply).  The latter appears to be in excess of 100Euros, which is considerably more than I want to pay.
Any suggestions on where to look ?  I'm not interested in a wireless solution, as it is likely to be used in places where signals are not reliable.
Thanks
Adrian
--
To Reply :
replace "bulleid" with "adrian" - all mail to bulleid is rejected
Sorry for the rigmarole, If I want spam, I'll go to the shops
Every time someone says "I don't believe in trolls", another one dies.