Pass Labs sells factory-built First Watt amps, as well as panoply of Pass Labs amps. A great source is Mark at Reno Hifi. Mine was built by a guy who took the plans that Nelson Pass has generously made freely available for DIY folks. This fellow then sold it to me for the "price of the component parts." That is, he did not build and sell it to me as a commercial endeavor for profit, which is antithetical to the intent of Nelson Pass in making the First Watt designs available to DIY guys.
I will hasten to add that if you are DIY-inclined person, the build of the F5 can clearly be done for a fraction of the cost of a factory-built version and is consistent with the desires of Nelson Pass. The rub comes when folks use his detailed designs to build his amps for commercial profit. Reselling such a First Watt as I acquired at the "cost of the component parts" is copacetic, so far as I know. Others can clarify this understanding.
I will hasten to add that if you are DIY-inclined person, the build of the F5 can clearly be done for a fraction of the cost of a factory-built version and is consistent with the desires of Nelson Pass. The rub comes when folks use his detailed designs to build his amps for commercial profit. Reselling such a First Watt as I acquired at the "cost of the component parts" is copacetic, so far as I know. Others can clarify this understanding.