[Stocker]

Remove either battery cable and put a 12vdc test light (or multimeter if you have one) in series between the cable and the terminal. Since your battery is discharging, the light should be lit. Start removing fuses one at a time until the test light goes dark, and you've found the source of the current draw.

There's another similar method that might be easier. Leave the battery connected. Place your test lamp across each fuse location as you remove fuses one at a time. If the light stays dark, it's a good circuit. If it lights up, that circuit is drawing current.