If you have a hardware programmer and specifically need a .bin file, you can extract it from the official .exe provided by HP: Download the (v1.27) from the HP site.
However, I can give you a to obtain the correct BIOS file for the HP Compaq dc7900, identify the correct version, and flash it safely. hp compaq dc7900 bios bin file link
Summary
Websites like forums or The Lab One sometimes host verified dumps. However, for the keyword "hp compaq dc7900 bios bin file link" , many results point to programmer-ready BIN files (including ME region and GbE region). Only use these if you have a hardware programmer. If you have a hardware programmer and specifically need a