I soldered together a pumping station and mounted the assembly to some home-made wood brackets. I was able to borrow the expansion tank from a friend, and I used the pressure relief valve off a spare water heater we have. The rest of the components (temp gauge, Taco pump, and fill/purge valving) were purchased new. The parts cost around $130, so together with the collector parts we are at about $250...a small price to pay for a lifetime of heat (and the satisfaction of watching the bottom fall out of Exxon stock someday).
Ready for installation next weekend!