Amazon do a few for < £2 with accuracy stated at +/- 1 degree. I have a few of these and they're all pretty close to each other at room temp.
I also have a couple for about the £8 quid mark from Amazon - a wireless one and a max/min one. Search my posts for the links.
If you want better accuracy (and one you can calibrate) I believe the Thermapen is the one you need at +/- 0.4 of a degree. Mind you, you pay for that ---> £50+ quid <gulp>
+/- 1 degree will do me just fine! :lol: