If it is indeed the rubber causing the squeaking
you can buy a silicon base rubber/weather strip
treatment/lubricant and apply it with a Q-tip
to see if that quiets it down.
You might want to try taking a thin slice of
quality hand soap and rub it in the rubber grove,
I have a clothes dryer that the rubber drive belt
starts squeaking every 6 months and handsoap shuts it up.