Basin Flange Extension Ring

I had a leaking tap in the bathroom and after an extensive search I found it was the tap itself. So I decided to buy some new ones, only they turned out to be longer than the originals. This left about a 2mm gap at the bottom of the flange when I put them all back together. I couldn't find longer ones in the hardware store so I decided to make a small ring to go under the existing flange and fill the gap.