What hot shoe should I use so they can work together?

[jawsy]

I don't think it will. If it does, it will probably only fire at one power setting. The camera can't 'talk' to the flash.

[GateCityRadio]

They'll work. But it won't do TTL. like Jawsy said, the camera can't communicate with the flash (and vice versa) to do TTL flash metering. I used a p-ttl flash with my sony A7 in manual mode and the camera had no problem triggering the flash.

[clackers]

The Sonys use a standard hot shoe these days. As others have said, your Sony can't drive the TTL on that model ... the other Pentax flashes will support manual. I use a 540 on my A7.

[UncleVanya]

Auto Green mode should work. That mode is not dependent on the camera directly. Green mode is for 6-12 feet and at ISO 400 calls for f/11 and at ISO 100 f/5.6 - extrapolate from there or use manual mode. Chart on the flash should be reasonably accurate. I have not tried this however.