I claim the ornamental design for an adjustable pistol stabilizer, as shown and described.
FIG. 1 is a back perspective view of an adjustable pistol stabilizer showing my new design;
FIG. 2 is a front perspective view thereof;
FIG. 3 is a left-side elevation view thereof;
FIG. 4 is a right-side elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a front elevation view thereof; and,
FIG. 8 is a back elevation thereof view thereof.
The broken lines depicting a lever and clip are included for the purpose of illustrating environmental structure and form no part of the claimed design.