Two suggestions - both require that you have a scroll chuck.
Method one: can produce a handle as long as the between-center length of your lathe. First turn the handle blank between centers, to put a tenon on the end opposite the ferrule end. Then, remove the tailstock from your lathe, and mount the blank in your chuck. Center as best you can (you won't have the tailstock to help align the blank in the chuck). Then, hand-holding the jacobs chuck with the drill bit, drill the hole. I suggest drilling in steps starting with a fairly small bit because that would be easier to keep centered, and then increase bit sizes in small increments until you get to the final size you need. Use standard twist bits - not brad point, spade bits or forstner bits. Drilling the first hole will be the challenge, but it should center reasonably well. Subsequent drillings just expand the size of the hole, and standard twist bits will center in a smaller hole.
Method two: more work, but you can create a handle of any length you want. Turn the handle in sections, putting a tenon of each section that you then glue into a mortise glued into the end of the next section. Obviously, the sections can't be longer than the maximum length you can mount on your lathe when using a scroll chuck on the headstock and a jacobs chuck in the headstock. You would probably want to design the handle to either have a pronounced discontinuity (a bead or a cove) at the point where you join sections, or else to turn the diameters at the mating tenons/mortise ends as closely as possible, and then after gluing everything together, mount the finished handle in your scroll chuck and spin on your lathe without the tailstock while you sand those joints smooth.