The Ready State Virtual Mobility Coach is like having a virtual Kelly Starrett in your pocket.
Agree with Rich. There must be something in your daily patterns or biking mechanics that is causing the problem. You should be able to identify and correct such an issue with a (very) good practitioner. The Muscle contraction technique I suggested above is simply to help maintain corrected position but won’t identify the daily patterning issue that is causing the SIJ pain (if indeed that is the problem).