radiator recovery tank

go universal

http://www.ebay.com/itm/New-Universal-Radiator-Coolant-Overflow-Bottle-Tank-Reservoir-603-001-/400917659830?hash=item5d588e00b6&vxp=mtr
or if on chev chassis this may work
http://www.ebay.com/itm/GM-OEM-Radiator-Recovery-Tank-15595742-/121546066453?fits=Model%3AP20&hash=item1c4cb5ca15&vxp=mtr

Radiator overflow/fill reservoir is a generic item. Just approximate the same tubing run, mounting tabs, and size.

The recovery tank is probably by the chasis builder. So you need to know what chasis is under it. Somewhere it must tell the make and model of the chasis (you couldn't even get brakes, air cleaner, oil filter or any other similar parts for it unless you knew the chasis make and model). And being that it is 26 years old you're probably going to need to go to a junk yard with the year and build of the chasis to get a recovery tank.