While there is a specific need to purchase the correct rubbers for certain areas of cars such as windscreen rubbers etc. there are quite a number of commercial everyday rubber applications such as spat rubbers which can be purchased from non original suppliers for a fraction of the cost of genuine articles.
While doing up the Winjeel I had to replace a number of cockpit seal rubbers. Now the Commonwealth Aircraft Corporation [CAC] made heaps of military aircraft in WW2 and post war made Mustangs, Sabres, Winjeels, Jindivik target drones etc. Obviously they were military oriented and there is no civil aircraft aftermarket support as you get with Cessna, Piper, Boeing or Airbus.
I visited Universal Engineers in Virginia who used to be M.P.O'Rouke in Bowen Hills. They still sell assorted rubber strips and mouldings primarily to the bus, truck and trailer body building industry. However they advised that Clark Rubber in Sandgate Road Virginia also had a good assortment and would be worthwhile checking out.
To my surprise they were correct and at Clark Rubber, Virginia I was able to obtain all of the rubber sections I required. In addition they were quite willing to give me small 50 mm samples of their rubbers to try/fit against the problem seal area before I finally settled on the section that I needed. I found them most obliging and they also sell in fractions of a metre. Their prices weren’t too bad either
Please note that not all Clark Rubber stores stock the same items as I am advised that they are now a franchise system. The local store near me does not have the range I found at the Virginia store.