Dynathrust 24DC3 battery

Nucamp does not install the batteries, the Dealer does the installing , and generally when the unit is sold . The dealer can choose whatever battery they want to install to "get the unit out the door" . Some dealers use cheap batteries, and some use good batteries . Dynathrust is just a re-labeled battery from one of the major battery manufacturer's. Sometimes its hard to tell what manufacturer or the quality on re-labeled batteries some dealers sell . Dealers usually buy batteries in bulk on pallets , so price dictates what brand they purchase to install on new units . 

You can either get the same "labeled" battery from the dealer , or just find a close replacement elsewhere .
Its a very common battery type. Its an RV/Marine group 24 series deep cycle battery . Likely around an 85 amp hour . Just like the dealer , you can buy a cheap one, or a good one . Look to spend between $75 - $150 , again depending on the name brand (on the label), quality, durability, longevity, and warranty .