I am curious what multispectral sensors are available for the DJI S1000 and if there are gimbals for these sensors that would work with the S1000?

The s1000 & S900 are highly customizable drones.  I don't use multispectral cameras, but I am using a couple of Flir cameras and Modified DSLR for ENDVI.   There are couple of types of gimbals you can use that will allow multiple types of cameras.  You just need to figure out first what camera you want to use and then chase a gimbal for it.  Some places will offer a package of camera with a gimbal.