Hi Chris
Probably not helpful, but we have just purchased a ESR-505C from Omnipole.
On this unit the hose is about 6mm id. We use the EZ Snap / Rectus fittings from gardiners with 8mm mini bore hose. As the hose wall thickness is quite thick, I managed to push an 8mm end stop into this hose with boiling water and a little brute force. Clamped with a jubilee clip it's working fine.
Only problem we have is what to do with the tap when the backpack is on one's back. Currently we wrap is round our necks so the tap rests on our chest for easy operation. Problem is when conector leak, even just a little. I see some have resorted to triggers on their poles, but that's for another time.
Spruce