Source for Nitrophyl Foam (for fuel tank/carb float)?

Hello,

I need to make a float for a scratch-built low fuel warning light in one of my motorcycles and have read that Nitrophyl foam is what would work best as far as material goes, but I haven't been able to track down a source. is anyone here familiar with it?

A little more background; the float will be doughnut-shaped and have a few very small magnets to trip some reed switches housed within the tube the float will be going up and down on with the fuel tank level. I could use another material if you have any suggestions. I've searched around online and haven't found very much information, but I know this is a very diverse and educated crowd, so I thought I'd give it a try. Any suggestions or comments would very much appreciated.

Thank you,

Rick