Reddit mentions: The best automotive replacement battery trays

Sure.

• Inverter - https://www.amazon.com/dp/B0007NOUBA/
  
  
• 2 x 75Ah batteries - https://www.amazon.com/dp/B00OZMVI46/
  
  
• Double battery box - https://www.amazon.com/dp/B07QJ2MBRD/
  
  
• 200amp ANL fuse & fuse holder - https://www.amazon.com/dp/B079ZNGCDX/
  
  
• Wiring - 1 pair of 4AWG 1ft & 1 pair of 4AWG 3ft - https://www.amazon.com/dp/B071H7D7SM/
  
  
• platform stool to keep equipment safely off the ground - https://www.amazon.com/dp/B072KDDS51/
  
  Should be about $750 for lots of runtime, and compatible with any pump that uses 120VAC. The only open question I have is whether the eyeletts on the battery terminals are 3/8" or 5/16" so I know which wiring set to buy. I emailed the company and waiting for a response.
  
  I used this guide to figure out what I wanted to do - https://www.tripplite.com/support/how-to-select-and-install-inverter-charger-for-sump-pump
  
  EDIT: wow thanks for the gold, kind Internet stranger!

Dual batteries is something on my to-do list, but don't know if it'll ever become a priority. I'm kind-of a budget-minded overlander, and have this dual-battery stuff in my Amazon jeep wish list for "someday"...

M.O.R.E. JKDBT0709 07-11 Jeep JK Dual Battery Tray (I realize you said your's is a '12)
T-MAX 47-3800 Dual Battery System

If its really stuck go to an automotive store around you and see if you can find a battery terminal puller.
https://www.amazon.com/Suuonee-Battery-Terminal-Removal-Bearing/dp/B07VD5LTMW?ref_=Oct_UPriceC_15708861_4&pf_rd_r=KS7ZV0PGTB1V3DB1TSJJ&pf_rd_p=a0e5ebfc-c454-58f3-ade7-e3394b7c5963&pf_rd_s=merchandised-search-6&pf_rd_t=101&pf_rd_i=15708861&pf_rd_m=ATVPDKIKX0DER

They work great for stuff just like this.

I got this one. It was a bit thicc to reach the bolt on the frame side, so I had to file it down, but I like how it looks, and it does the job.

I have done this on a old Cyberpower. This was about 10 years ago though.

BUY A SEALED BATTERY BOX!!!!! https://www.amazon.com/Moroso-74051-Sealed-Battery-Box/dp/B003JOZ3QU

I did something similar to this http://www.instructables.com/id/Rework-a-UPS-with-Massive-Capacity/

Word of caution: The cheap UPS unit melted after 12 hours of run time on the 3 batteries I had attached to it. I lost power for about 3 days and i had it attached to my fishtank. Lucky i had everything in a metal pan and nothing cought fire just a epic smell that was still there when i moved out of that rental..

The Factory RPO code for two batteries is 6A6. Hopefully this can give you some info on where to start. If you want, I can go take a picture or two of my 09 PPV and show you how it was set up.

I was also able to find the OEM second battery tray on Amazon.

Probably something like [this](NOCO HM306BK Single 6V Snap-Top Battery Box for Automotive, Marine, and RV Batteries https://www.amazon.com/dp/B00316KU6E/ref=cm_sw_r_cp_apa_aMDlzbAS57HBM)

here you go