It's very easy to start your own starter. This LA Times article on starters was surprisingly good:
Organic, whole grain and rye flours have lots of "wild yeasty beasties" and enzymes that give a starter tremendous oomph. Which is why I recommend the use of rye flour or rye grain to begin any starter, even if you make white flour bread or whole-wheat bread. Moreover, the wild microorganisms present in/on rye flour and grain are already adapted to growing on grain, according to Raymond Calvel, one of the big bread starter gurus.
Fruit juice (pineapple juice, specifically) in lieu of water can aid a starter because of its addition of acid (to keep non-beneficial microorganisms from growing) and a fermentable sugar – a tip from Peter Reinhart.
If you keep your bread fermentation relatively cool (below 85 degrees F), your bread will be sour and rise quite well. Over 85 degrees, and your bread will be more complex than sour, and will have diminished rise and carbon dioxide. Lots more info on starters here on Chowhound. Good luck!