Can anyone recommend a good online source for different thicknesses of gasket rubber?

I lived in Mexico for two years in 2005-07 and there was a local shop that sold every thickness and variety imaginable (Mexicans, apparently, make a lot of gaskets). I stocked up before leaving, but last year finally used up the last of my supply.

I've only been able to find one local hardware store that sells different varieties and it's very expensive so I'm hoping to get a better idea online.

Yeah, I would really love an online contact too. I have tried eBay (which I posted about several months ago) but have had no real luck.

Can you buy from Grainger? http://www.grainger.com/category/rubber/raw-materials/ecatalog/N-ay4  I know in the US they have warehouses locally but you can buy via catalog or their website.  Marine shops often sell it also. http://www.go2marine.com/product/52213F/rubber-gasket-material-by-the-square-foot.html?WT.srch=1&WT.mc_id=gb1&utm_source=googlebase&utm_medium=productfeed&utm_campaign=googleshopping&gclid=CJCe68ew7LwCFTBgMgodFXsA5A

Grainger seems to have a Canadian site. I hadn't thought of Marine shops, so I'll look in to that too.

Thanks Shawn!