linda,
the inline filters are readaly avaliable at most bike shops, they are usualy hanging on the wall behind the parts counter, just ask for the inline filter, you need 1/4" ones, which means that it fits nicely into a 1/4" fuel line. although i agree with two tired, i hate them too, but if you have an old tank that has a bit of rust in it... it is a good idea to have them. the carbs can only push so much of that crud through.
the problem i have with my 500, is that there is so much crud in the tank (from a failed cleaning with improper chemical) that the petcock gets cloged (the top inside where the fuel has to find its way through the really poorley designed little tunnels with several right angle turns... so... you might want to take it off, and make sure its clean, compressed air is the best way, along with some carb cleaner, but careful to limit the cleaner to the rubber parts.
good luck, i missed a vintage ride yesterday because of the same problem... bike cuts out after the gas in the bowles runs out...