Kal at Appareo tech support was very gracious about revealing the connectors used on their Stratus units (I was shocked frankly as companies can be difficult about these sorts of things).
Here's the transcript:
ADS-B Connector
Connector Type (to Stratus): MS-151-C(LP) connector
Connector Type (to antenna): Reverse Polarity SMA
If you are looking to make your own ADS-B antenna cable, these links may be helpful to you:
Sporty's sells a 10 ft ADS-B cable with a reverse