https://www.ebay.com/itm/16-Metal-Bo...-/252717312707
I would think any "press on" valve stem seal would be ok.
You use a thin plastic guide like a condom over the stem so the seal doesn't get damaged by the collet grooves, then once the seal is on far enough, the plastic guide can be removed.
The seal is then driven on to the guide with an appropriate seal drift.
Whether you use .502 or .500 , your choice.
Is your stem size 11/32?
Gary