I've got one of the rubber antenna mounted on the wing, whilst it's not stunning, it's more than adequate.
So the question is, why isn't your installation working as well as others?
If a replacement aerial is fitted, ensure that the surrounding metal on the underside of the wing is taken back to bare metal before connecting the antenna to ensure a good earth, after installation, re apply paint etc to stop rust.
If you can get the radio out, there's a small tool usually, just connect a replacement aerial and dangle out of the window. That should improve reception.
Of course, it could be the radio that's faulty!!
It can be fiddly getting the antenna through the wheel arch, then dashboard to radio, but with a little patience, you can do it.
Companies that install radios in vehicles will remove the radio for a small charge. Only takes 30 seconds, or find your local scally, they take radios out all the time, they probably have a better radio for a small fee!!!???
PS, If you get really stuck, I could help during most week days if you fancy a little trip out??