I don't have Cruise but did have that rattle in the lever.
Problem was, partly from the brass bushing being worn but also where the lever glides inside the master cylinder, was worn wider.
I first tried an O-ring to snug it up but it wore out quick even with lube.
Then I went and used my very-old Wagner brake grease. This stuff will slow a snail to an amoeba's pace, it's that thick.
Ace Hardware has "flat springs" that will work quite well.
G.L.!
