It is my opinion that these are TERRIBLE solutions. I go between Phila and NYC and see them. My impression is that they are invitations for others to bump park off your car. Also, they don't cover the bumper corners so what is the point of having a clean center but ruffed up corners!?
The only thing I can suggest is using bumper strips that NY cabbies use; thick and long and mounted via double sided tape. Doesn't look very pretty but can be strategically placed and match painted. Im not sure where they get them b/c I can find those exact ones. You can also try to be adventurous and look at home depo/lowes for inspirations. Honestly, if you choose to live in a city and can't afford a parking space, you have to accept the fact and think of bumper covers as wear and tear items that need to be repainted every X number of years (X so you can plan for it). Enjoy life and your car. Repainting a bumper is not that bad if you shop around or have the appropriate insurance premium to cover it.