Syncro/ LT Mirrors

[Hairyface]

Hi folks, hoping you could assist. Many moons ago I bought a set of LT mirrors off eBay. After storing them in the shed, I have decided to fit and have had them powder coated. Having looked at the wiki, I am unsure how to fit exactly. The mirror has a part number of 291 857 513/514. From looking at the photos on the wiki it would appear that I am missing the bottom gasket that covers the arm to the bracket. Can this be purchased separately. I have bought a new lower mirror bracket and mirror gasket from Brickwerks but can't seem to see the part that covers the bottom of the mirror arm to the mirror bracket - or am I being completely daft and missing something obvious. Thanks for your help and apologies in advance if this turns out to be a completely insane question.