Plastic wheeel with magnets

I'm looking for a company that sells magnetic encoder wheels. Such as below. Anybody know any place ?

you should fill in your location, might be easier for people to recommend suppliers if they know where you are.

what dimensions are you looking for?

I'm in Detroit MI by the way. The dim is 1" diameter

use iron wheel with gaps/holes and one permanent magnet in series
with the sensor

As nbucska said, it is often easier to use a permant magnet pick-up sensor, like those used to drive a speedometer , along with a slotted wheel, or gear. You can even use a metal disc that you have cut slots into. I have done this on trucks, using a drive shaft U-Joint 's four wrist pin ends as the "wheel", or a balancing weight on the drive shaft.

You may need to do some shaping of the waveform, since it will be similar to a sinewave, but that is easy to do.

They are called "inductive or magnetic pick-up senders " and you could even get one from an auto scrap yard for cheap.

if you want to make one yourself this might help..

**broken link removed**
they should fit nicely on a one inch disk..