Electrically it shouldn't be a big issue.Is there a way we can rewire the horn so that it works without the key in the ignition? Is there a risk of draining the battery?
vicHarbor Freight has some cheap, but effective dual horns.
https://www.harborfreight.com/2-piece-12-volt-electric-horn-set-99911.html
I put a set on my wife's 1995 Buick. They sound like, and the loudness is similar to traditional Detroit car horns. The included relay can used with fused power directly from the battery to wire the horn to work with key off. The OEM horn would be disconnected. The negative switched OEM wire will need to be tapped for one side of the horn relay coil.
vic