Wondering if it's a secret

I need to get an oil pan plug for 97 RR 4.0 and nobody here has one. So, I'd like to find out the diameter of the plug if anyone knows so I can find something to plug up the hole (gum? earplug? maybe a self-threading universal plug?).

Just wondering if anyone here can help me. Truck's sitting in a private and soon-to-be-hostile parking lot in a pool of oil.