<3 my SKS.
As Adam said, Zack’s has some nice MFS zinc-plated steel cased non-corrosive ammo 500rds for $150-170. My SKS loves it. Plus, it’s non-corrosive so you don’t have to be a Nazi about cleaning it immediately after shooting.
I wouldn’t worry about detachable mags on it. If you convert it to accept detachable mags, you’ll be limited to running 10 round mags until you make the gun 922r compliant. Look up online the parts needed, as I never looked into it. I like the factory non-detachable mag on it because it feeds reliably.
Check out Firefly Firearms (guy runs it out of his house) in Schenectady. If you’re on NYFirearms, he’s on there. He also has a Facebook page. His prices are really good on the Gen 3 stuff from what I understand, not sure about Gen 4. B&J also has good Glock prices.