I took a broken one apart and made a new one out of leather. Mine only had one hole at the bottom from which air entered and exited. I would assume that is why there is a space between the bellows hole and the inlet in the bottom of the smoker.
You should drill a hole the size of your spring half way though the wooden parts for the spring to sit into. This will keep it from slipping sideways.
One other then to think about when making a new bellows. You need something to go around the outside edges of the bellows covering the edge of the leather to keep the air in. I had planed on using the "trim" from the old bellows but soon found that my leather was thicker then the rubber/plastic used on the old one. So the trim would not fit correctly. It still works fine, I just stapled the leather to the wood. It does leak some air though. If you come up with something to use for this please let me know. I have not really put much thought into it as it is working anyway.