Here is a standard flange WR-42 waveguide broadwall directional coupler made by Aircom, high directivity type, 18-26 GHz, 16 dB coupling factor.   If you are interested in 24 Ghz hamband experimenting , you may have noticed how expensive and relatively rare things are. I figure this is a good item for the tinkerer and experiment that does not want to take out a new mortgage to buy stuff.   Have fun!