I have seen a few guys at races with a spout on their gas containers that act as an automatic shut off when you pull the container off of the gas tank. Most are aluminum looking.
I have what you want but couldn't find what it's called - it is made by Premier Motorsports Racing. (602) 867-8293 according to my Dirt Bike mag but I got mine from a local dealer.
It is not a particularly fast fill but it is extremely easy - just make sure to wipe the filler otherwise you will get a slow buildup of dust in your tank.
I've got one that I use during my pit stops. Only problem is a buddy gave it to me and I don't know the manufacturer. It's purple and gold anodized and works great, won't spill a drop and emptys pretty fast.
Mine is like Smittys, but I don't know who makes it either. I've seen them for sell in the ads in the mags for around $120. They're usually by the fuel can ads.