They make universal ones at the parts stores. Pretty cheap, some are even chrome if you're into that sorta thing. I don't know if all Ford stuff is the same, but I'm pretty sure dipsticks are reasonable standard so I'm sure you'll have no problem finding a SBF dipstick tube.
If you buy a dipstick and tube that are a different length from your stock one, make sure you use the matching dipstick and tube, otherwise your readings will be way off.