Velcro strapes / ties in good quality and at reasonable prices. Velcro tape ends are available in several different lengths and widths, both as hook-and-loop and in whole rolls, so that you can cut to the desired length yourself.
Velcro is familiar from most homes and can be used for almost anything when it comes to holding things together. It works exactly the same way, where you put two surfaces together, where one side has microscopic loops of threads (the soft side), and one side with small barbs (the rough side).