Looking for small motor shaft brake

[Kjelt]

In some steppermotors and servo's there is a brake built in. It is actually just like a car wheel brake it fits around the axis and clamps the axis when powered or better when unpowered, preventing the axis to move even after the power to the motor has been cut. Very handy and convenient when there is some static load attached that will move the axis.

Small motors do not seem to have those brakes, yes you can use a high ratio (1:50 or higher) gearbox , still the sideeffect is the slower response.
So I am looking for a small affordable (<$20) brake to fit a 6mm or 8mm axis, preferably for sale in standard production , so not a 2nd hand one off, from ebay.

Do they exist ?
Does anyone know where to buy them ?

Thanks.

[i_am_fubar]

Look for shaft electro magnetic clutches. Same mechanism.

http://www.chaintail.com/dry-single-clutch-brake-micro.htm

[Gregg]

It depends on the specific motor, of course, but it shouldn't be too hard to put a reduced current DC on opposing coils of a stepper motor to make a magnetic brake.

[IconicPCB]

Depending on the "small" motor look into mobility scooter motor shaft brake.

[I wanted a rude username]

How much backlash can you tolerate?

If the purpose is safety rather than locking the shaft tightly in position, you could use a pawl similar to how automatic gearboxes park. It's reliable, reasonably strong, and the part tolerances are high.

[Kjelt]

The purpose is functionality that the axis does not start to move itself under the load after the power to the motor is off.
I like the  electro magnetic clutches website it also has permanent magnet brakes, those would do the job.
Now lets see where I can order them for testing.
Thanks people