Homemade door closer to keep localized heat in room

We decided to follow the idea of heating ourselves rather than the house this cold season, but wanted to keep the bathroom slightly warmed (nothing like a cold seat!). The doors kept being left open though, so we hung a towel in between one door and its outer corner, and for the trickier other door, a towel hung slightly over the door (the weight to pull the door closed). I rubber banded this towel to some old plastic since otherwise, the friction the towel made was a problem. (The rubber bands had to go between the layers of plastic so they wouldn't make friction either)
Here are pics!

all I saw was red x's..

would a bungee cord work too?

Sorry about the images. Hopefully they are all good now.

And yes, a bungee would definitely work too.