Graynomad:
For years now the pumps have been integrated into the tank, at least on vehicles I've seen, so that would be a very easy way to do it.
For those of us who don't want to buy the tank too, there are usually generic aftermarket pumps which are designed to be fitted inline with a hose. There should not be any problem finding a pump on its own, if that's the preferred solution. (Personally, I'd take a quick trip to an auto dismantlers and expect to pick up the whole thing for a couple of quid.)