Are there any alternative GPS modules for the Pentax k30 than the O-GPS1?
A true alternative, one that supports the full features of the O-GPS1 module, is very unlikely as the biggest thing lost would probably be the astrotrace feature (one that I miss with my switch to Nikon). There are, however, some options out there:
In both cases, it requires some level of processing to update the image with the GPS information. The first one is a lot more manual, the second one less so, but it's a need. If you have the O-GPS1 unit, it just happens, something to keep in mind.