Has anyone found an adhesive or solvent to bond NinjaFlex?
Some rubber adhesive, perhaps?
Bonds pretty well with Ninjaflex. 
3M 5200 adhesive marine sealer sticks NinjaFlex together, but it is by no means structural. The bond strength in tension is maybe 15% of the material strength.
I must admit however that the tube I used was very old.
I have yet to find any commonly available solvent that has any effect on NinjaFlex.
I just use a soldering iron to heat and seal flexibles. Not the prettiest but it works.
You can find some industrial chemicals if you Google “TPU solvent”
hi adam
E6000 is crystal clear, flexible, vibration and water proof.