I used to have a bunch of them for the 250. Too bad I think I just cut up my last one for something last week.
Try HomeDepot plant/pump section. They sell long pre-filter 2-pack for $9.99. It may work for you and give more filtration. They may not have the end fitting bt you should be able to find some strainers at J&L or even HomeDepot to thread into the end of your pump.
Good luck, I will also let you know if I find some in my stash of stuff.
I know landscape centeres sell them at rediculous price. You may find them at hydroponic store cheaper.