I happen to know a little something about these cars The power antenna has long been discontinued, the aftermarket "universal" antenna is not a very good replacement but it does work with alot of effort and some fabricating of brackets. There are a couple routes you can take to fix this, I will explain the easier. Remove the front right wheel, and elevate the car as much as safely possible. Next remove to inner fender bolts enough to allow you to pull the inner fender away from the antenna area.
Disconnect the antenna (under the hood by the fuse block, its a 4 wire connection that looks pretty big and grey) and then open the passenger front door, you will see a nut with a washer that looks like a star (in the middle/crack of the door jam) remove this nut and the antenna will drop down. the new one will require transferring the old bracket exactly as it was on the old one so pay attention. you will also need to make your own bracket to help support this new one in place.