For anyone averse to using complicated mechanistic approaches to solo toprope, it is easy to rig a prussik to self-feed along the rope by dragging a pulley underneath it. I.e. both the prussik and pulley are clipped into your harness. Loosen the prussik enough to feed, then as you are climbing, your upward movement causes the pulley to push the prussik up the rope, without tightening. When you weight your harness, the pulley falls away and the prussik tightens, catching your fall. Since you are on toprope, you shouldn't have to worry about overloading the prussik. Oh and you do need to weight the hanging end of the rope to facilitate proper rope feeding.
I've used this system several times, and its one drawback is the need to re-loosen the prussik knot when you want to continue climbing.