I have an 1986 Free Spirit Tourney bike from Sears at home that is pretty worthless as a bike (plan to use it to learn/practice how to build/true wheels) but I think it might have some clips used for cable routing that might work for your application. What diameter is the tube you're routing along?

...Just throwing another idea out there... If you can leave the cable on the bike and disconnect both ends where the lights and batteries connect, you could get away with zip-ties for the cable and leave that on the bike but remove/install the lights/batteries only.