I certainly have been aware of the industrial sized 2 and 4 sided planers but have never seen a smaller 4 sided planer/moulder.
Logosol a Swedish company makes a really neat small 4 sided planer/moulder. While not exactly cheap the prices are much cheaper than I would have expected. (Que Darcy to come in and point out he bought a Stetson-Ross for $300, 4 tanks of gas and breakfast at Denny's)
It seems they also make and brand them for Woodmizer as well if you want an orange one.
http://www.logosol.us/planers/ph260/
https://woodmizer.com/us/MP260-Planer-Moulder
Attachment 387616
It does 2 and 4 sided @ ~10" and single sided at ~16".