What products are similar to rubber, but don't use petroleum?

[TransAm12sec]

I need to find out a product that uses a substitutes for petroleum. Something along the lines of windsheild washer blades.

[animal]

I thought I read once that there is a rubber tree or something that you can get it from just inside the bark or whatever. Not sure tho as that was many years ago.

[SSScottSS]

I'm not 100% positive, but I don't think silicone contains petroleum. http://www.flexfab.com/Techdata/why.htm