Thanks for the reply. I don't have any specific suggestions for mono sensors, but something APS-H or larger would be nice.
I recently read this from someone on Cloudynights:
"The only true mono CMOS sensor with microlens in 36 x 24mm format, is made by Nikon as a microscope camera.
The product number is DS-Qi2, it has 7.3 micron pixels, 4908 x 3264 array, 77% QE, 60,000e full well, 2.2e readout noise."