No repository that I'm aware of.
I purpose built a banquette sleeping pallet that goes from LR corner to end by covering half of one wheel well.
The top is hinged in the middle to access 2 storage bays within, and at the head (above the well) I put a door to get to the reduced stowage space there.
The foot of the bed also has a smaller hinged lid, beneath which I installed the necessary...
Otherwise, inspiration is to be had by reading others' build threads...
Those who say that it cannot be done should not interrupt the people doing it.