same as gaza, you don't need to buy another pole just drill a small hole near the top of the fin section and a large hole at the bottom of the handle and feed the tube through,
when doing this ensure that you fully extend your pole and have at least 2 mtrs of extra tubbing hanging out of the end
i do the above with my 18ft pole
however with my 30ft pole i run the tube on the outside as it is not used to often and when not in use i leave it rolled up in my van.