Nasa has something called a GAS CAN, which is a small payload that can be purchased on a shuttle. Information: http://sspp.gsfc.nasa.gov/gas/gas.html
Pricing is typically pretty expensive, and the program is on a space-available basis. Since the shuttle is still grounded, it's unlikely that the next flight will take any GAS cans; all payload will probably be taken up with more essential scientific programs.
That said, the best way to get it up there at this point is to have it hitchhike with an astronaut or cosmonaut. Or you could launch it with a satellite, but that would also be costly and a one-way trip.
