You can make a wrench pretty easily with a torch.
Get a 3/4 inch combo wrench, the cheaper the better. Heat and bend both ends right at where they join the center handle. Bend to 90 degrees.
Use your torch to cut an opening in the boxed end of the wrench to slip over the spark plug wire. Cut and grind smooth to 1/2 inch opening.
Use a 3/4 ratchet to loosen/tighten the spark plug wires or use an adjustable wrench on the main handle if you prefer.
I see the photo is a bit out of focus, but you get the idea.
Scott