If you know of someplace where you can find or buy an old-style float and arm style toilet valve, that arm is often copper or brass, and the diameter will fit in most soldering irons. Cut off small sections and file one end into a tip.
If you want REALLY budget tips, I have been known to buy a screwdriver or two from the local hardware store that sells cheap junk. Found one with a shaft diameter that fit and cut it into sections with my Dremel. No, it doesn't work as good as a proper tip, but it'll get you by while you save up for a nice tip.