The Northern Tool & Equipment Co. has a lot to chose from. I bought mine from there.

http://www.northerntool.com/

Here's the one I bought.

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_396428_396428

I just added a section of hose to put in the truck gas fill tube and the other end just sits in the gas can. Might work for you might not, seems to work fine for me. Just a suggestion.

I also have a funnel that has a long wide round opening(10in across by 12 in deep) as opposed to the short traditional funnel design which allows me to pour large amounts at a pretty fast pace. I do hate the new design gas cans that they make you buy now, does anyone know of an adapter kit or a hose to replace those stupid fill tubes?