This is a minimal filler tube - its made from 40mm PVC waste water tubing about 75mm long. A shallow grove is cut all the way round. The loop of nylon cord allows weights to be tied on.
Shot showing internal spacer - about 15mm thick super-glued to both the outer (PVC Waste) and inner (clear braided flexible fill) tubes.
Balloon Neck pushed over the filler tube - Totex balloons are a tight fit.
And secured with a cable tie that sits over the grove.
For Hwoyee balloons fold the neck over and tie.
The grove and the cable tie ensure the neck is well secured.
Depending on the diameter of hose used you should be able to attach it to the “Balloon inflation valve” BOC/airproducts provide by heating the pipe by a hairdyer and pushing it as far as it will go over the valve. Wrap with a little insulating tape after for a better seal.