Well, I have a Cannondale MTB with oversized tubing. I am able to mount my bell on the bull horns on the end of my handlbars. It's easy to get to but also out of the way.

It seems like I have to make every bracket I need for that Cannondale!

And it depends on how crappy looking a job you can live with. Hose clamps work fine, but makes your bike look more like a beater. Wood works fine too, and it's fairly easy to work with.

Be creative!