Salvage yard, find an early 2000 Mercury Marquis or Ford Crown Vic. You're looking for a pair of horns (dual tone) with the PN# AM80-S on it. Most will have the AM80 set.
That's not what you want.. Grab the right ones and make sure you get a good 4"-8" pig tail from the old ones. You may be lucky and have the same plug but my 93' I had to rewire. Your horn also may be in the front grill area, mine was under and in the fender lining under the battery.
Not much of a write up on it but if you go to a recent post [#35] or
https://ford-rangers.com/forum45/74.html you'll see what I did.
I don't think I would go out of my way to say it was "twice" as loud, but mos def ridded the truck of the "beep-beep" Mattel truck sound.