Is something like swapping out the seats from another camry/Avalon/es300 possible?
doing it with a motorized seat will be more trouble than its worth maybe

 

1996 to 2001 Camry was the same generation.

Avalon was upscale Camry.

Rear seats of ES300 may be different.

A motorized seat will fit but there will be no chassis connection for it. May also need to rewire seat belt switch connection to work with chassis connection.

 

if you cant find a set for the 98 at wreckers or private sale online

worth asking a local upholster or shop around

you might get a good deal on new leather coverings over the original seat frames