For inexpensive boards with uBlox modules, look on ebay for Reyax. I have two different models and they work great. As far as I can tell, the two boards that I have are using real uBlox modules, not counterfeits.
Some of the uBlox modules can be programmed to output a signal from 0.25 Hz to 10 MHz (or more). The default is 1 PPS. If you don't need or want the serial data, just ignore it. Using uCenter software, you can disable any and all output messages that you don't want.