I am the OP,I spent a whole(rain) day on the inter-net and phone trying to find an "o" ring or the size of the "o" ring needed.1/2 in.QD's are suppose to be ISO compliant...Contacted Snaptite,Foster,Parker ect.,dealers,distributors ect.NO-ONE had and o-ring or knew the size.Auto parts stores didn't have the correct one.My Kubota dealer couldn't even help me!
I finally found a Mom-Pop old time dealer that matched up my o ring in about 15 minutes of going thru their inventory.
Every-one wanted to sell me a new QD,crazy for a 50 cent O ring.
There are lots of places on the net selling "o" rings ,if you know the correct size.Like JJ said try and measure a wrecked "o" ring some time.I do own a digital caliper and know how to use it.