Now that the E is back from the body shop and the ugly parking lot dent is gone from the fender, I finally got around to repairing the antenna tip. (To be honest, all this time I've had part of a drinking straw, flattened at the tip, covered in electrical tape with some silicone at the bottom...it worked fine for the interim and didn't look that bad. A friend of mine who knew it was broken thought I'd already fixed it until I told him to take a closer look.
Okay, while I said I'd take pictures and do a DIY, I didn't plan on doing this today, but I was over at my sister's house for Easter and got into it after washing the car. So I didn't take pictures. That said, I'm not sure exactly what I would take pictures OF (except perhaps the end results). It's pretty self-explanatory, so I'll just expand on Jamie's cursory tip.
Remove your antenna cap and CAREFULLY remove the gasket (as Ed mentions, it's pretty brittle, if you break it I'm not sure that is separately available, but mine is looking a bit peaked so I'll inquire at my stealer) and then remove the bottom piece of your old rubber tip from the inside of the cap.
You'll ultimately need a half-inch drill bit, but I started with a 7/16, then to 15/32 and then I noticed that the bit had moved a bit off-center (which made me glad I started smaller, had I started with the 1/2 I would probably have ruined it). So I used a small blade on a pocketknife to even it out, then used the half-incher. Even that was not quite
enough, so the pocketknife finished the job. I also ended up cutting off about 1/4" from the bottom of the new tip where it flares so greatly; otherwise the assembly will not seat properly on the base.
The only real
issue is that it is barely too short; in order to reach the next ring/rib (see close up shot) on the new tip you would have to drill bigger, then you'd be off of the top and into the body of the cap, which would ruin the cap. Thus it puts a small bend into the antenna. But since the antenna's usefulness has passed and it's only for show at this point, it's no big deal (plus the little bend shouldn't affect it anyway).
There are two pics so you can see the results, one from a bit farther away and a close up that shows the rings/ribs on the euro design. It's not perfect but for under ten bucks it looks better than an exact replacement -- and it's plainly better than a drinking straw, electrical tape or not.
Take care and enjoy the ride,