Where to buy Rotary Encoders

Hi ^^ I wanna build a pendubot for my university. I decided to use rotary encoders for an absolut angle measurement. But the problem is, i can't find any contactless rotary encoder, does anyone know where to buy them ? I can't use a Potentiometer or sth like that, because of the friction. This is a Pendubot: http://www.youtube.com/watch?v=Wz1t7McSnUg

Thanks

Not sure if this fits your budget, but these guys make really nice optical encoders: http://www.microesys.com/

They tend to somewhat expensive for hobbyist use, say $50 and up. However if you search out E-bay you can find bargains once and awhile:

http://cgi.ebay.com/BOURNS-ENS1J-B28-R00128-OPTICAL-ENCODER-/370489013259?pt=LH_DefaultDomain_0&hash=item5642ddb40b

Lefty

Hi, thanks for your replies^^

I found some encoders by clicking on a shop advertiding button on ebay .

http://www.megatron.eu/SMC3/plugin-transformer?trafo=live&plugin=doc&mode=designin&tp_subRulesID=1206567953264&language=de&objType=doc&gclid=COPdyOLV6KkCFZUS3wod-xtWag#ajax0&false&designin&LoadDocument&&de&doc&1234867270725

Don't know why Rotary Encoders are hard to find and Gyros you can find anywhere ????

http://www.amtencoder.com/