If you do an internet search for ADAM-6510 you'll find a 4-port 10Mbps Ethernet Hub for approx $100.
Hubs are fine for general small LAN ethernet traffic. This device is 10-30vDC Powererd.
Practically every hub or switch I've seen below 16 ports is DC powered with a wall wart of some kind. This expands the possibilities. I haven't seen a significant difference except in price between "consumer" and "industrial" and have used selected (metal cased) "consumer" gear for years without problems. 24VDC isn't very common, but 3 terminal regulators are. YMMV
GarrettCom is a California manufacturer of hardened Ethernet switches and hubs. If you would like more information, my phone number is 510-580-2396 and email is [email protected]