Isn't the fan relay in the under-hood fusebox? And go to a junkyard. Lebaron sedans, Plymouth Acclaims, and Dodge Spirits are identical to your car. All the other EEKs will have usable parts as well. But leave it to Chrysler, who made all their cars so nearly identical, to change the most minor and unnecessary details from car to car. The overflow bottle is one of those ridiculously-changed details. In fact, between identical car models with the same engine, some have different bottles. Still, you have a VERY good chance of finding an Acclaim/Spirit/LeBaron Sedan in any junkyard.
By the way, the temperature sensors should be right by the thermostat housing, I assume you changed the thermostat yourself, so just check to see if they (I think there are 2) are plugged in and not broken.
So look in that fuse box.