It sounds like you have an OS top tube with a 34.9 diameter. Is that right? Normally, the dimension is given in diameter rather than circumference.
I prefer cable stops to guides.
I got two of these for the same purpose:
https://www.treefortbikes.com/Interl...ing-Stop-286mm
They come in all different sizes including 34.9.
If you just want cable clamps, something like this might work:
https://www.ebay.com/itm/Stainless-C...m/323818275757
Get the ones with the screw rather than just the clip. The clip rotates and looks like crap.
If your top tube is really 28.6, there are more options, including getting the cable at 7 o'clock on the tube rather than along the top at 12 o'clock.