If you use the link to zooplus fishadmin posted in this thread, then look for the Eheim air pumps, the cheapest one would probably do you, it comes with air stone and tubing and is adjustable. The others have twin outlets which are independently adjustable if you want to run two air stones etc. I haven't got an eheim air pump but I have got filters and gravel cleaners and they are vg, Eheim is v reputable manufacturer.
If you do get it, will be interested to hear how you get on with it
[url=http://www.bigfishcam