I think we’ve used this self-adhesive foam tape somewhere on every robot for the past 7 years. It’s been part of the team’s prototyping process when trying out various intake mechanisms, it’s made it into “production” on many of them, and has been a quick fix for moving pieces that slam together too hard when reaching hard stops (hard stops being a future blog post – we can’t live without those, either). It has just enough “squish”, isn’t too thick, and is pretty durable. When it’s worn out, it’s not hard or overly expensive to replace.
It’s available in your local home center, usually in the plumbing department of all places, because it’s used to insulate pipes. It does cost $15-$16, but I think we’re on our second roll since the team has started.