Reduce 5v Trinket Pro to 3.3v? Apparently these nRF24L01+ modules need 3.3v, but I've only got 5v Trinket Pros that I'm using.

How can I reduce the voltage to the RF transmitter?

Would a voltage regulator work? Specifically looking at this: http://addicore.com/product-p/165.htm
The NRF24L01+ has inputs that are 5V tolerant! So you only need to provide 3.3V on the Vcc pin of the module, which you can do by putting a voltage regulator between it, and the 5V of the Trinket. So there isn't really any need to convert the Trinket to 3.3V.

PS Remember to add some capacitors to the output of the voltage regulator, as the NRF needs a pretty stable 3.3V. Noise in the power lines can cause instability in the operation of the device.