E-trailer has a couple options for pull out battery trays. You would need to change cables to make the system work. Tray runs $250 or so, then add the cost of the longer cables.
The Flow-rite battery fill kit for two twelve-volt FLA's can be had for $68, and the hand pump is another $25 on Amazon. When we installed ours a couple years ago the price was around $80 for the whole system.
2018 ACE 27.2
Toad 2019 Jeep Cherokee Trailhawk
Roadmaster Falcon All Terrain Towbar