model 2880 Tefal, i can't shut it?

After putting water in the iron i have to put a stopper which allows the the iron to presurise. I am looking for the stopper as the one i have has it's rubber broken so if i try to shut it , there won't be any presurisation, thus i have to use an adjustable spanner to lock and often i over tighten it. If i touch it by hand i can get scolded by hot water i would like to get the proper devise for shutting it, please help