Guest AlYou say you're looking for a travel instrument? Is the ability to take a few bumps is an issue? If so....
I once played in a band with a cello player who had an aluminum cello. It sounded great! It originally had a simulated wood paintjob, but he stripped it down to bare aluminum. It looked mega funky. I also procrastinated on responding to a classified ad and missed an opportunity to buy an aluminum bass. I regret that one to this day.
Aluminum violin family instruments were manufactured mainly for school use where durability is an issue. They apparently concentrated on basses and cellos, but did make some violins and violas. Check out this page .
The odds of finding one are probably pretty slim, but wouldn't an aluminum fiddle be way cooler than a plastic one? Strip that sucker done to bare metal and you're guaranteed an audience any time you pull it out. *G*
Bruce