I mounted the cup holder on wood then attached bathroom hooks (used for towels or robes) and it hangs off the window tracks. My DW didn't want me to put hole in the wall. You can also do the same, but mount a small storage box to hold your items.
Dave, U.S.A.F. (Ret)
2019 Fleetwood Discovery LXE 40M (Big D)
2016 Ford Focus, flat tow