Good luck, not many people get rid of these ranges other than the cook top breaking or becoming damaged.
There are many places that sell used appliances who may have one around they are gutting for parts.
I know of a guy, Don, who runs a used appliance place in Las Vegas called Buy/Low Appliance that has a very large yard filled with used appliances that he pulls in and repairs as room in his small sales floor becomes available. He has more used appliances in his yard than any place I've ever seen in my life. I haven't been in Vegas for several years so I'm not even sure he's still in business (he's been around for years, but he was getting pretty old even back when I knew him).
He often gets appliances donated to him that are in exceptional shape for some kind of program he has with charity organizations like Big Brothers and Big Sisters. I guess its worth a try to call him and see if maybe by chance he has a cook top for you around. He isn't the kind of guy that likes to just give stuff away though, so I don't know what kind of deal he may give you if does happen to have one.
He's old school, doesn't even own a computer I most likely, so you'd have to call him during normal business hours. Not going to hurt to try I suppose...
Buy/Low Appliance
5730 S Boulder Hwy
Las Vegas, NV 89122-7402
(702) 433-4020
Otherwise, try a google search and see what comes up as far as used appliance parts. I know of a lot of techs who regularly check web sites like craigs list looking for broken appliances people are selling cheap or just giving away that they pick up, fix and resell, so they are certainly out there, just a matter of timing and luck finding one.
Those glass tops sure look nice, but what a hassle and expense, I don't know if I'd ever own one myself. I like my Montague commercial open top gas burners with convection oven and flat griddle too much. | 
