Playing about with some knitting books from the library led to this belt.

The pattern is so ridiculously simple that I had it memorised after about an inch of knitting, and I share it here with you:
Cast on 6 stitches
Row 1: Knit three, yarn over, slip one, knit one, pass slipped stitch over, knit one
Row 2: Purl three, yarn over, purl two together, purl one
Repeat until it's as long as you want it. I found it easy to remember by thinking 'three stitches, increase, decrease, stitch'.
You can then either cast off normally, or to make a pointy end, I did the following:
Row 1: Knit one, knit two together, slip one, knit one, pass slipped stitch over, knit one
Row 2: Purl all stitches
Row 3: Knit two together, slip one, knit one, pass slipped stitch over
Break yarn and pull through two remaining stitches
Ta da!

I used Patons Washed Haze Aran (an aran/worsted weight cotton and acrylic blend) and 4mm needles. And a buckle I found in my button box.