2010 Chevrolet Malibu Transmission Pressure Control Solenoid Troubleshooting

2010 Chevrolet Malibu LT 4 Cylinders B 2.4L FI DOHC 146 CID
MH-8 6 speed automatic transmission-Reverse gear and 3rd gear doesn't engage-a check engine code showing one of the solenoids is stuck.
The pressure control solenoids were filthy from old fluid- I believe this is why it became stuck.
I've cleaned the solenoids well, but I've run into a problem. When I removed the solenoid assembly from the computer part, some of these yellow plastic pieces fell out of place. I have put them back in place, but I am left with this concern about some O-rings.

In the image you are looking at one side of the solenoid assembly-
It has these little O-Rings with a strange reddish membrane, on 3 of them. 1 of them has no membrane. It was either lost or that one by design doesn't have one-either way I do not know.

I imagine the 4th one is supposed to have the same red membrane. If so, where can I find a replacement?