Whilst it's very similar to the idea of heat shrink, I've found that silicon tape is perfect for this task. The tape I'm referring to is non-adhesive but will stick to itself forming a permanent bond.
I've cut myself on the sharp cable tie ends, the heat shrink didn't lay flat sometimes and electrical tape can leave the adhesive behind.
A short piece of silicon tape can be wrapped around the belt; it's soft, flexible, permanent and can still be removed easily. YMMV of course.
This stuff is also great for cable management, connecting dodgy vacuum hoses, keeping USB connections tight, makes great non-slip handles for tools and comes in several colours (black matches the X-Carve nicely of course). Stretch it whilst you're applying it with a nice neat 25% overlap and it looks great as well.