I have had these things for years so I am describing it off the top of my head, not in front of me.
The short peice of webbing you are reffering to is attached to a small plastic cover that Sea to Summit have produced to fit inside the tap to prevent accidental spillage. Neither the cap or the webbing are neccessary, in my opinion, if you are careful with how you pack the bladder.
The only thing holding the tap in place is a carefully cut round hole in the fabric-sized perfectly so that the lips/ring on the outside of the tap prevent it from falling back inside the bag. Thats all.
So the bag is pretty simple. Even if you dont get the hole right, I wouldnt worry about it. You can just make it slightly bigger and find the tap whenever you need it. Or just dont cut a hole and open the zipper to access the tap whenever you need it. Remember you will need a zipper or some other access to get the empty bladder into/out of the bag.
Hope this helps, I would send you a picture but it would take about an hour on my computer and dial up internet.