The parts you require:
2 x Endcaps that fit the ends of your footpegs(depending on the style of footpegs and make of your buggy).
2 x Pop-rivets or 4mm capscrew,washers and nuts.
2 x 500mm x 50mm webbing.
2 x 100mm x 10mm webbing.
2 x 500mm x PVC tubing, not to stiff so it can still bend.

First take some time to measure your particular setup. I have provided rough measurements for the materials required but you might require to trim them to suit your setup. Take in mind that the footstraps are there to retain your feet from bouncing off... not to tightly strap them to the buggy as this will result in twisted or broken ankles if not worse.

Fold the 50mm strip of webbing in half and sew along each side to form a close ended tube, at the same time sew the loop of 10mm webbing as pictured. Burn a hole at the closed end and trim it using a soldering-iron. Insert the stiff tubing into the opening left at the 10mm loop side. The purpose of this is to hold the strap open to put your foot into it at any time. The little 10mm webbing loop is basicly mounted on the fork above the footpeg similar to a larks-head knot. You can prevent it from sliding up and down this tube by using a simple wire-tie. The other and can be attached to the end of the footpeg in a variety of ways. The end of my footpeg is just an open ended tube which I used to close off with a plastic endcap. I simply pop-riveted the strap to the endcap with a washer on each side in order to prevent the rivet from pulling through. As all buggies are different I'll leave this part of the attachment to your creative imagination but I can suggest that you can use either a velcro strap or the same 10mm webbing strap on that side if required. What I find nice about this strap is that the plastic tubing inside it helps keep it open and that it is simple and sturdy enough to last.

This is how you put it all together.

Modify at will!!!