On my 04 GX there is a small storage bin in the back - open the rear door and look along the lower back trim panel in the cargo area - driver's side. A couple of plastic tabs to press and the cover pulls out. The special wrench and a cargo net were stored in there when my car was new. Could be 'most anyplace by now but that's a place to check
The posts prior to yours were about GX470 models. Have you checked the jack/storage area (in the GX the jack is stored in the compartment shown in the photo). If you can't locate it here are a couple of ideas:
1) a lot of tire stores around here have a pretty good collection of the special key wrenches - they could remove the locking nut for you and you could replace with regular lug nuts. On mine it's only 1 special nut per wheel
2) in the owners manual folder in my GX there was an order form - it has the # of the wrench that matches the locking nuts - and an order form to mail in and buy a spare or replacement wrench
Another method is to get 4 regular deep sockets that are just a wee too small to fit over the locking lug and sledgehammer them onto the lug nice and tight. Then proceed to remove the lock lugs with a long torque bar. It will ruin the lock lugs and the four sockets but at least you will get them off.
I had to do that once in an old car of mine when I lost the lock lugs. That method does not work at all if you get the Porsche 'pin' style security locks with the spinning sleeve.