Sorry to hear of your predicament.
I didn't even know the oil cooler has a drain plug. Are the drain plugs on 90 - 92 model year coolers only? I had my oil cooler out and flushed it out with mineral spirit but didn't notice any plug.
Ebay has a used 90-92 oil cooler plus AC condenser for sale.
http://www.ebay.com/itm/90-91-92-COR...9SPMoP&vxp=mtr
Also, a new one but listed as for 93-95 ZR-1.
http://www.ebay.com/itm/94-95-C4-COR...UkygPw&vxp=mtr
Does anyone know what the difference is? If it's just bolt hole location, I would buy a new one for later years and modify as needed.