We claim the ornamental design for a radio remote control unit, as shown and described.
FIG. 1 is a top and front side perspective view of a radio remote control unit showing our new design;
FIG. 2 is a top and rear side perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The evenly dashed broken line representation of items in the figures is included for the purpose of illustrating the unclaimed portions of the article and forms no part of the claimed design.