I just did this last week and went to NAPA auto parts and purchased two vacuum caps in case of future use of the original mount on my 09 SG as well as the tourpak mount and they look good and are not noticable as well as it was like $2, I am guessing one of the cheaper things you will ever put on a HD. They come in many different shapes and sizes, I went with one a little shorter and smaller diameter and had to really push it on but it will stay on without anything securing it plus its a little shorter.
I've been wondering the same thing. Actually talked to a buddy of mine this weekend about it. Wondering can you take them off and maybe put a plug in the hole?
truck stops have the little vinyl caps that they use for cb antennas. they're cheap and if you like black or whatever color, they will likely have them. not a bad idea to use some sort of adhesive like 3m tack and trim adhesive though.
Can anyone tell me what the thread pitch is on those? The dealer is telling me 6mm X .25 but I can't find where that exists. I'm not near my bike for the next two weeks, so any help would be great.