A couple years ago I bought 2 Liebert GXT2-6000RT208 backups for our shop. Got them on eBay for a few hundred each - with the shipping I was right about $450 each but these retailed new for close to 3 grand. They are big commercial grade 4U rack mount units. Being high end units and the size they are - they do require 220/240v input which can be single or 3 phase which is nice. Depending on the output PDU module installed they can be hardwired, or have a combination of multiple 120v and 220/240v outputs. You can find nice size commercial grade units on eBay pretty regular. Shipping is always going to be high due to the weight but you end up with a very high quality UPS for a huge discount. Our Mimaki JV33 running with the heaters on can keep on printing for close to 20 minutes on one of the 2 6000va ones we have. The other provides backup for our main RIP computer and the cutter. These have saved us far more than what we paid for them in jobs not lost during power outages/flickers over the past couple of years. Quite a few times jobs have finished in near total darkness in here - nothing but a few machine led lights on and lots of beeping from UPS's.
A HP latex machine has a LOT bigger power demans than our Mimaki though. I believe those use dual 220v connections and have some pretty hefty heaters in them so for a battery system I'm not sure what size you might need to hold your printer for long. I'd guess you woudl want a combination of a beefy commercial UPS to handle the instant outage and load plus a generator to pickup to load within a minute or two of the outage. A generator by itself would be nice but it it has no battery backup to hold the load till it cranks up anything printing will be ruined anyways.