I claim the ornamental design for a portable lubrication unit, as shown and described.
FIG. 1 is a perspective front view of the portable lubrication unit showing my new design, having a cover in an open position; and,
FIG. 2 is an alternative perspective front view thereof, having a removable lubricant supply container mounted on the portable lubrication unit for delivery of the lubricant therethrough.
The broken lines showing various features in the drawings are for illustrative purposes only and those features form no part of the claimed design.