If you flip to line-in and slowly flip back to radio, maybe you can get radio to work?
That particular switch is no longer available. It is a leaf switch that is mounted next to the function selector switch (looks like a record bar). There is a lever on the side that slides forward/backward as the function switch is thrown. The movement of the lever actuates the leaf switch that turns on the amp. Similar leaf switches are available new but aren't an exact fit. Somehow, you'll have to figure out a way to retrofit one mechanically and aligned to work when both line and radio functions are thrown. Perhaps you might be able to fiddle with the switch and get it to align better so it gets thrown in the radio position but if I were a betting man, my money is on the switch being on it's last legs. Doubtful that fiddling with it will result in a lasting reliable repair.
