I cannot tell the voltage rating or the frame size from the description, but here are a couple of alternate stepper motor manufacturers that probably will do...

Steppers are sized by a NEMA standard, and as long as the voltage rating is the same, you should be okay with picking an alternate.

My guess is this motor is driven by a bi-polar chopping drive, so you should take into account the maximum current rating of the motor as well, which you indicated is 3A...

http://www.pacsci.com/products/step_motors/generalhybridproducts.html

http://www.linengineering.com/line/contents/stepmotors/

http://catalog.orientalmotor.com/advanced/stepping-motors--1068/pk-series-stepping-motors?

Hope this helps,

-Dave