yes I do have the outlet cover

 

I believe there is a threaded ring that holds the power accessory outlet in the dash. It threads on the backside of the outlet and if it came loose, it should be on the harness still plugged in on the backside of the lower dash piece.

 

Not sure if it's different from 97 to 98, but the outlet on my '97 fell out. I pulled the lower dash portion to fix it, and found that there was a threaded sleeve that fit over the power outlet. It was threaded at the end where the wires attach to the socket, and to secure it in in place, you just fit the socket to the outside of the dash piece, and screw on the sleeve from the wire end and sandwich the dash piece in between.