a bit of an odd question but someone maybe able to help

Bearing and seal place. Run in there with the thermos bet they have something to fit it.

Cheers

Go to Clarke Rubber and find the right profile of rubber. If you cut at a 45 degree angle and glue with super glue. A bit fiddly getting the size right but it is possible.

if it a round profile you will buy off the shelf.

Neil

If it is an Aladdin or Stanley email the manufacturers website in the US and they might send you a new cap and /or seal. I've done it with an old Aladdin one and the posted one over gratis.
Might be worth contacting the Aussie agents/distributors too.

hi
if its an aladdin mine has a flat profile rubber seal last time i replaced mine
i bought a toilet cytern fat rubber seal to suit and cut the hole to suit the alladdin screw-in stopper and then cut the outer diameter to fit into the stopper recess using a sharp razor knife
mine is an -- aladdin industries nashville tennese -usa -no 11 stopper

looked at mine its due for a new one so will do same again
you wont get a flat seal at the bearing places as im sure they only sell o-ring style seals but i could be wronghope this is a help
cheers
barry