I've been perusing these forums for quite some time now and figured it was time to contribute something that may come in handy for someone down the road.
I recently planned a kegger at home as a going away for a friend. I decided to buy a 58L sankey keg of PBR to accommodate this and as such ordered a sankey coupler to use with my current draught system in lieu of pumping air into the keg. This way, if we didnt drink all of the beer it would not go bad and I could finish it off myself during the following weeks.
Well.. a problem arose with the shipping of the coupler. Long story short, I had to rent a "Bronco" pump from the beer store. I figured I was capable of figuring out how to mod it as to be able to still use my CO2. My goodness, it was a pain in the ass.
After an entire afternoon, This is what I came up with. There is a relief valve on the side of the pump that can be taken apart. I took the pin out of the center of the valve which left direct access to the cylinder of the hand pump. I took the step-down nozzle of a caulking tube, cut it to the right dimesions, jammed it in the hole and secured it with lock-wire (this was the final of several failed attempts). I then used that part as a quasi hose barb and Bob's your uncle! It worked beautifully with my pony bottle all night and required zero pumping. We never ended up finishing the beer and I now have it in my kegerator. The beer Gods were very pleased with my efforts of saving he precious nectar.