I mentioned before Christmas that Aphrodite gave me a nail buffing kit, and then I got another one as a gift too. So I'm a firm fan and I think you should be too!
You can get these fab little items in most chemists - I have a Mavala set and also a buffing block from M&S which is a brilliant to pop into your bag in case of any buffing emergencies. God forbid that you should see a bit of a nail ridge whilst on the bus of a morning!
The Body Shop have a nice one for about â‚¬6 (it's there on the left), Opal London (who are great for various little beauty bits and bobs) do one too, and Boots will oblige you handsomely as well. The Ms Manicare range they stock is really cute and there is a handbag friendly 4 way fold-away buffer that should cost about a fiver. If that doesn't suit, Boots also do an own-brand 4 way version which will cost about six quid.
None of these buffing blocks will cost you in any way even near a tenner, which is great value for something you can use over and over - and which is truly effective.