How to attach cable mounting points to a bicycle frame? I have a frame-building project that is near completion: An old 90ies steel MTB frame was cut, and converted into a frame for a cargo bike.

In my enthusiasm, I have overlooked one detail: The original routing of the shift cables (shown in the photo below in green) is not possible any more, because


the frontal mounting points near the position of the former head tube were cut off (schematically shown in blue in the attached sketch), and
the cargo beam is attached below the bottom bracket, and therefore takes/blocks the former place of the shift cable guide.


My idea is now to re-route the shift cables along the top tube, as schematically shown in yellow in the photo.

However, I'm still missing the mounting points. If possible, I would like to avoid removing the paint and start welding again. Are there any options, like some cable casing mounting points that can be attached with screws, clamps, or something alike? 

Since I believe that this could be interesting to any person that likes to tinker with old bike frames, I'm putting my question here.
I'd go with full housing for both brake and gear cables and hold the cables on with cable clamps. There are many kinds of cable clamps to choose from. I prefer the type that have a screw clamp over the clip on type. The key will be finding clamps for your tubing diameter. 

If you need to have cable stops there are clamp on versions from a variety of vendors. problemsolversbike.com has a variety of solutions for tricky problems.

Items linked are examples and not endorsements.