It's possible, but there wouldn't be a Toyota part number or any way to verify (other than ordering std stuff and then checking to see if it interchanges). Back when these vans were still in the yards I would grab the fuse boxes out of them. I brought my wire shears and took as much wire as I could easily get along with the connectors. When I need something like that now I just take the connector and attached piece of wire, then butt connect that into my harness.
I'm betting you could find the right gauge wire with the right spade on it in almost any Toyota from the 80's & 90's. Just go to a salvage yard with a pair of dykes and snip snip away. Tim