turbocharger elbows

Where can I go to buy 90 degree bent elbows(rubber)thats a transition from 2" to 2.5"?

High quality silicone can be found here:
http://www.slowboyracing.com/DIY/Silicone%20Hose/Silicone_Hose.html

Otherwise, I'm not sure where you could buy a regular rubber one... try looking in the phone book for a Rubber place. Alaska rubber or something like that has a lot of misc pieces that might help you.
You might try a 2'' elbow then put a 2''-2.5'' reducer after it.

www.sporthoses.com is BADASS. Those things are 1/4" thick, and same prive as the thin stuff. Another popular one is www.hosetechniques.com, and www.DiamondStarMotorsport.com also has some. Most are the thin style inlcuding SBR. Sporthoses has the thick ones. Doesnt really matter they both work.