Modify FPGA image for MPS2+ using the Cortex-M33


I'm sorry if this question is somewhat obvious, but I cannot find an example or anything online. I want to change the example SSE-200 (AN521) image to better support some work, but I cannot find any of the source files that went into making AN521. Is there a repository somewhere that can be compiled into that example? If not is there some other example that has a Cortex-M33 core on the MPS2+?