We used to make our own O rings by using the correct diameter rubber cord and a dot of Super Glue to join the ends. The same process could be used on that torque tube nut seal if necessary to prevent having to dismantle everything. Square O ring material is also available instead of round stuff if you do a little internet searching or you have an industrial gasket and seal supplier in your area.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!