The tab in the floorplate is going to snap anyway, so snap of off if it's not already snapped. Then get an aluminum rod about 1/4 in. in diameter and bend it into an L, and rivet the foot of the L to the floor plate. Now drill a slant hole through the floor plate and through the bottom back of the mag body, so that when you replace the floor plate, you use a self tapping sheet metal screw to keep the floor plate in place, doing the job that had been done by the flimsy tab. Cut the height of the top Of the L to get the right capacity, it arrests the downward travel of the follower.
Now you can take the mag apart for easy cleaning.