Cleaning corrosion is easy. You can just scrape it off with a very small thin straight blade screwdriver. After I had all that I could possibly get out then I'd look to see if where the contact went it was then attachable again. Usually they are just a slide or snap in situation anymore. See if there is anything you can do. Otherwise you can solder the spring back in. But you'd have to make sure you got every little bit of acid off the metal. It is easy but you can only use but a touch of solder. You have to find the smallest gage (which is the highest number. So 20 is thick, but 28 is like string. If you can't maybe your husband can or ask around to your friends and see if anyone can for do the soldering for you. Some one who makes stained glass can solder and of course anyone who tinkers with electronics but maybe even a gear head.
Otherwise about any tv, dvd, bluray electronics in general repair shop can do it for you. I'd just call in advance and ask how much.
But someone said copper. Copper is the best conductor. See if you can find sheet copper and cut it into a square the size of the space where the previous conductor was. I've never tried that because I can solder but it makes logical sense that if it in is contact with the space where it was it will work. Rio grande jewelry making online might have thin sheets.
And maybe just putting it in place not attached and putting the battery in carefully will work. I use to do that as a child. Just then tape the batteries in place best you can so they don't move. If the battery cover holds them thight then you don't have to tape.
Well good luck. I know it's salvagable but it might be difficult.