The trick will be in getting taped up, but the tension part is easy.
Here's a commercial unit which should give you an idea on design. Scroll down to the picture of the strap:
One alligator clip would be attached to the tape, and the elastic band would go down your leg to wind around under your knee where the other alligator clip would be attached to the band to secure it. A safety pin can be used to prevent things from coming apart as you walk and cause tension to shift.
Using a band with adjustment capability such as on suspenders (braces) allows you to fine tune the tension.
The website has a video demonstrating everythings, but I couldn't get it to load properly this morning.