Cat “Ecology Valve” Part Number 173-0566

I'm putting this here in wheel loaders but am guessing Cat uses these other places. This is used as a drain valve on the finals of a 980K W7K loader. This is a valve like those Cat has used for years on Hyd. tanks and transmissions. After removing the drain plug one then screws in a pipe nipple to off seat the valve and drain the oil. All the ones I have seen in the past use a 1 inch pipe nipple to open the drain, these are smaller and use a 3/4 pipe nipple. They work fine and make draining the finals an easier and less messy job. My problem is the plugs have an oring on them and SIS does not give a breakdown on them. Also would be nice to be able to order a spare plug in the off chance one is damaged or lost. Price for complete valve is just short of $200.00 US! I will try contacting dealer and also check to see what size these thin orings are in the morning, just wondered if anyone has done the work before me. Thanks for any ideas. Ken in NY