There a ton of resources for undyed plant fibers online... just do a google search and you can find them.
Here are a few people that I have ordered from in the past and recommend:Undyedwww.coppermoose.com
and he is on ebay has great prices and is very dependable. He has bamboo top and tencel for great prices, undyed. I have also seen Faux Cashmere on his ebay site so be sure to look at both of them.
I got some great hemp from www.spunkyeclectic.com
for a reasonable price. She has all kinds of great things so it is definitely worth looking!www.littlebarninc.com
is another great company also that sells ecospun (recycled water bottles) and recycled denim, which are very interesting non wool alternatives and a fun spin. They also have nylon, hemp, flax and linen that are not dyed. While I was getting this link, I see that they have dyed cotton too!Dyed
If you are looking for dyed bamboo roving, I will be posting some either later this week or early next week. I also dye tencel but don't have any right now to dye. I plan to get some dyed before Christmas but we all know about the best laid plans...
Mandie from www.EweGivemetheknits.com
also sells dyed bamboo and soy and is amazing. You have to move quickly as hers sell out very fast. Her prices are great and although she is in Australia, you would never know it because she ships so quickly.
Another good friend of mine, Sandy from www.homesteadwoolandgiftfarm.com
sells dyed cotton roving for REALLY great prices. Be sure to check her out if you are looking for cotton. I think she is one of the few that sells it dyed.
There is an etsy seller, fiberlady? Shhe also sells dyed bamboo roving and I know people who have been pleased with her product although I have not ordered from her. Here is her link: http://www.etsy.com/shop.php?user_id=5056259
Ok, well this should keep you busy for a while!
Happy spinning to you.