This is a latching towel holder and two of them can easily hold a wet towel for proper ventilation and drying. The model is held to the wall / door with a command hook double sided tapes and you can get from here.

To hold the towel raise the notch and slide the towel in and then lower the notch. The towel gets wedged in between and held by its weight.

If you want to customize here is the model in onshape . You can take a copy and edit as you see fit.

This is a print in place mechanism with enough clearance and you should print on the side  with support enabled. The pivot area need some support which I as able to knock off easily. Support will help with cleaner print and smoother movement of the notch.

NOTE: Please use 100% infill for strength and rigidity.

If you print and use this please share your make!