since I bought my e30 last year, i've been really eager on removing the universal type antenna installed as it doesn't retract and it's not fitted properly but i can't find an original replacement(second-hand of-course). I don't listen that much on AM/FM so the replacement is just for cosmetics, I've seen a couple but they're always missing the important bits. After checking forums I decided to just go with rubber plugs. it took me a while but I was finally able to get an alternative from Supercheap.
1" blank grommet, it's a tad bigger than what i need as antenna hole is ≈22MM(7/8" will be a better fit) but it's the only size available in the store
here's how it sits now