If you want, airsoft Gi, (airsoftgi.com), has a load of m58's in their broken/referbished section, for about 25-30 dollars. It is hailed as a decent sniper for the price new, (100$). Referbished/broken may be taking a risk but It might be worth it to you if you end up with a good 30$ spring sniper. They also have a lot of referb/broken UTG master snipers and super 9's, which kind of suck, but hey... Maybe it would be worth it to you to gamble 30$, maybe not... Just giving you a heads up and info, as the broken/referb items usually go quickly over there. If you are willing to take a chance and maybe put some time into one as a project gun, the reslts could pay off, or maybe you would get one that works from the start, whatever. Thought you might like to know.
Also!!! The JG sniper is very good for the pice, and though it may need some assembly, works quite well.