Size of O-ring used in the bearing cap

My driver came apart, and I somehow lost the O-ring used on the bearing cap. What are the dimensions of it so I can get a replacement?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0