Thanks for the tip, I did not consider other pressurized gases. Why nitrogen? After a quick Google search I examples of using C02 but not nitrogen...I'm wondering what the difference is.
For this application, Nitrogen, CO2 are essentially equivalent as inert gases, and so the difference will be 'what equipment do you have'?
As gadfly56 mentions, Nitrogen in its tank is at higher pressure than CO2, but for this application both need to be regulated and your flow rate will depend on the regulator you have.
CO2 liquefies under pressure, so you can get more mass of gas into a given size tank.
Other gases would be suitable but vastly more expensive (Argon, Helium, etc.)
The big thing is that the mouse doesn't create a tight seal and doesn't need much pressure, so you need high volume low pressure. If you a using bottled gas, some sort of air amplifier would be great, using the high pressure gas from the bottle to entrain air and get a high volume low pressure flow.
-Jon