I found the one for the brine piston (store here called Princess Auto). I put it all back together including the two other 'bad but not completely broken' o rings on the 'inductor?' part. It is working now and I'm back to having soft water without the tank overflowing or the brine coming through my taps! (big happy face) I'm going to keep looking for the other two o rings as I'm sure before long I will have another problem. However, they are at least easy to get to when I do find them! Thank you for all your help - not sure how you were able to give so much direction without actually being in front of it, but it sure was appreciated!