Can anyone recommend reflective patches that can be sewn on to a backpack, but where the reflective part is removable (i.e velcro)?

Generally I ride with a rack and trunk, but the new bike I'm looking at buying will require me to commute with a backpack. I'd like the backpack to have a bunch or reflective tape on it for visibility, but...

1. All the reflective tape I've owned always falls off, and

2. I also use this backpack for other purposes, and don't want godawfully bright refletive tape on it all the time.

Similar product suggestions welcome. Thanks.