The ornamental design for a boosterregulator, as shown and described.
FIG. 1 shows a front view of a booster regulator showing my new design;
FIG. 2 shows a rear view thereof;
FIG. 3 shows a right side view thereof;
FIG. 4 shows a left side view thereof;
FIG. 5 shows a top view thereof;
FIG. 6 shows a bottom view thereof;
FIG. 7 shows a bottom, front and right side perspective view thereof;
FIG. 8 shows a top, rear and left side perspective view thereof; and,
FIG. 9 shows the booster regulator and a tank with pressure gauges.
The portions of the design shown in broken lines in FIG. 9 are for the purpose of illustrating the environment only and form no part of the claimed design.