The going rate is $15 because on eBay they want something for it, and almost all charge realistic shipping. I was hoping for a freebie here I'd pay shipping. I am finding that other than eBay, these things are VERY hard to find. I am not sure Newegg has one but I know I am not going to buy a new one.
Check the disks you have to read first. I think those 5 1/4" disks went through an evolution similar to the 3 1/2" ones. There are later versions that are double density, so make sure the drive is capable of reading the correct density.