Is there a simple way to convert from a pull switch to a toggle switched light fixture?
The easiest-to-install solution to your issues is a length of 14/3 run in surface raceway and used as a switch loop.  You'll want a circular raceway box at the light fixture, and a single gang raceway box at the switch, by the way.

(Also note that the non-metallic raceway recommended by dfife's answer won't work here -- Legrand, for some reason, doesn't make round extension boxes for their non-metallic raceways, just for their metal ones.)

Diagram (originally appropriated for this Stack by Tester101 and reused here):