I've had good luck with an inner-tube and tape arrangement. I grind the handle so there's a bit of a notch at each end, to keep the improv'd handle from slipping. Then I slide a section of old inner tube over it, typically from a small tire. A length of bicycle tube could also be split and used as a wrap if the blade is too wide. Then wrap progressively tighter with good quality electrical tape; this will hold forever if protected from sun/elements. The outer wrap is hockey tape, the stickiest and most enduring cloth tape I've ever seen. The result is a grippy, cushioned handle that's darn comfortable to use, even though it looks pretty rough. I have one on a cut-down machete that has to be 10 years old and it's still going strong. Note that nobody will ever steal a blade with this kind of handle.