Thanks for posting very interesting. I really liked the info about your cattle and their water requirements.
I have a small generator but I have been thinking about a PTO generator. I have a small diesel 36 HP tractor.
This guy is a drivable distance for me to pick up.
St 10KW Gen Alternator PTO Gear Box Coupler Combo | eBay
I have been watching craigslist and natural gas one come up once in a while usually someone upgrading and the installer it selling the old one.
Or an office building but those are usually too big for me but would work for you.
You might fine a propane generator that a office building no longer needs on craigslist that would fill your requirements and not break the bank.