What are some options for a seatpost remote cables on frames without a pre designed route?

I'm considering a dropper post but would only do this if I was able to mount a remote as I like the continuous flow of being able to change things on the go.

The bike I spend most of my time on at the moment is a steel hardtail which under the top tube has a route for two gear cables and a brake hose (FD-RB-RD). I'm wondering if there was anyway to snuggly attach two lines to the brake hose hangers or if there is another tidy and safe alternative?