For basic handlebar-swing top tube and down tube protection, I've been using a 3-layer or so wrap of the same self-fusing silicone tape I use to finish up my bar wraps. It fits tight enough that I don't have to worry about it moving/rotating slightly, and also tight enough to not allow any dirt/dust/etc to sneak in underneath. When I've carefully cut it off a top tube after a stem reach/height adjustment changed the handlebar contact point, it's always clean as a whistle underneath. (Why do we assume whistles are clean? Aren't they usually in the mouth of humans, full of saliva and food particles?).

I don't know if they disperse enough shock to prevent top tube dings from actual crash-ups, but they make a reassuring dull thud noise on the stand, in the garage, at rest stops, etc.

I also do a silicone tape wrap at the bar ends, because when my bikes fall over, and they fall over even when noglider isn't around, it seems like the ends often hit first, and the tape/wrap gets torn there.