Not satisfied with my bodge, I quickly modeled and 3D printed a T-junction this morning. You can find it here: https://www.thingiverse.com/thing:5919964 You'll need to use hose clamps for it since it doesn't have the barbs, but I don't think there's much danger of it blowing off. If you get it printed, PETG, ABS, or Nylon would be the suggested materials.