the elastic band issue can be solved using Web Dominators, Carousell should be selling em for cheap, maximum SGD2 per piece.
the sternum strap prob can roll it up and use velcro strips to secure it, this will prob means there will be two bobs flying around whenever you walk but thats the best management for it i can think of hehe
Btw, u using Pixel3? I'm gonna sidetrack a bit, but can i ask if you have any complaints about the Pixel3? Thinking of changing my iPhone X to it.
PS: i'll not carry the discussion about Pixel3 too much in this thread, requesting for the guys to give me some posts here for it nia