Double Pulse For Each Incoming Pulse -> Double Stepping Stepper Motor Control
You could use a small microcontroller which doesn't require much external circuitry. One such option is a 8-pin PIC10F200 from Microchip. It's available in 8-pin DIP and 8-pin or 6-pin surface mount packages. It just needs VCC and GND, all remaining pins can be used as GPIO. It's self-timed with a reasonable accuracy, so it doesn't even need a crystal. Using a microcontroller gives you a nice amount of flexibility for solving the problem.

http://www.microchip.com/wwwproducts/Devices.aspx?product=PIC10F200