Yes, Midi Stomp would work great as an affordable controller for Sunday Guitar. We would recommend getting one with an expression jack so you can add an expression pedal for volume.
Sunday Keys Version 2
Using the Tonic Pad Player
Getting Started with Sunday Keys for MainStage
Troubleshooting Sunday Keys for Ableton
What Gear do I need?
Troubleshooting Sunday Guitar
My Song-Specific Patch is Different from the Demo
Customizing Your Song-Specific Patch
My instrument/controller isn't connecting