We claim the ornamental design for a support assembly for a gas cylinder, as shown and described.
FIG. 1 is a rear elevation view of a support assembly for a gas cylinder, showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a top, front and left side perspective view thereof;
FIG. 8 is a top, front and right side perspective view thereof;
FIG. 9 is a top, rear and right side perspective view thereof; and,
FIG. 10 is a top, rear and left side perspective view thereof.
The broken lines shown in the figures are included for the purpose of illustrating portions of the support assembly for a gas cylinder and form no part of the claimed design.