I've got a tap'n'die set from Aldidl - probably cost under a tenner, lives in a nice metal box, and has done me fine for several years apart from snapping the M5 tap through cack-handedness (now replaced with a single tap from, IIRC, B&Q).
For light use, anything that's not made of obvious cheese will be adequate. As torslanda and Kim say, the most useful taps for bike use are going to be M5 and (especially for you just now) M6 - the advantage of a set over individual ones is that you'll get both of these, and a holder. If you have stripped the boss, I'd run a 5mm drill through it, and then retap to M6 - once you've got the kit, it's a ten minute job at most.
As hubner says, take it gently and lubricate generously - WD40 or GT85 aren't exactly approved tapping lubes, but they'll work fine for this sort of job. Half a turn max at a time - less if you're getting a lot of resistance - then back off quarter of a turn, and make damn sure the tap is going in square - if it's off-line, it's more likely to snap.