If its jsut purely for waterproofing and not asthetics I wrap them in heat shrink and seal the ends with hot glue I have all sorts of sizes of 3:1 heatshrink all the way from 1" wide to 8" wide.
Here is my gateway thats sits next to me(took photo right now) the ends are not sealed but you get the idea
https://i.imgur.com/7dR4xZT.jpg