heat shrink for outside use?

Ok Guys

I know heat shrink is used for inside the car, I have also heard that they make a heat shrink for outside, with a sealer in it to give you a waterproff connection. I have looked for it at out local auto parts, (Autozone, Muray's) but can only find the regular heat shrink. Is there any other choice's? I have used the crimp connectors made for outside use but in this case I will be soldering wires of two different size's so a crimp connector will not work.

Thanks Mike