This is overkill and would be much cheaper from china, but heres a suitable transistor for 6.6 cents each: https://www.digikey.com/product-detail/en/diodes-incorporate...

Found on my phone in 30 seconds. In units of 100k you could easily find something for 2 cents or less.

Sorry to be critical, but I think that MOSFET is undersized for an application trying to save power. There are two issues, it is N-channel so will require a charge pump in order to use on the high side. It also has a rather high R_DS of 0.3 ohms. This means when switching (just) 1A, it will cause a voltage drop of 0.3V and will dissipate I*2.R_DS = 0.3W. 6% power loss when delivering 5W.

I'm in the middle of building an enclosure for a cluster of Raspberry PI like boards (~2.4A draw) and want to have software power controls. So I've been looking to do this...

There are specialized devices for this sort of thing from many manufacturers. I'm currently looking at devices from TI - TPS22958. It has a built in charge pump and an R_DS on of 0.014 ohms. So dissipation will be a lot less 0.081W at 12W power delivery, a 0.7% power loss. This of course comes at a cost -- even in the 10,000 of units it will cost ~40 cents a unit.