3 options I see as perfectly acceptable.
1. Create a 13/15 seat supreme court.
2. Divest the supreme court's power of judicial review
3. 1/3 of the Supreme Court Justices face a retention vote, every 4 years. (Meaning all Justices face a vote once every 6 years)
Me personally, I'd take both options 1 and 3. Option 2 leaves a power vacuum to be fixed.