That is probably the same horn used in my Port of Lionel City B unit, and it is indeed pathetic! Sorry, no help here!
This looks like a modern version for replacement parts for yours. 6-30189 from set 6-38236. it's a 2013 vintage
curiously, they list the two motors at different rpm's
I also noticed when looking at the supplement for the original version, that a foam pad was listed in the fuel tank. Perhaps that was the side to side buffer that was missing from yours. Anyway, you solved that.
Here is a youtube of the horn in the 6-30189
Respectfully, some of you guys are really overthinking this. I’ve done this type of conversion many times, mostly on GP’s (4 or 5) and 2 RS3’s with no problems. The electronic e-units have been able to handle the extra motor with no problem. One thing you should do is inspect and/or clean/lube the power truck. I had two trucks that had hair (cat hair I assume) and steel wool. What a mess!! An alternative, if you want e-unit only, is Dallee Electronics. I’ve used their product many times with no issues.
Steve
I know the original e unit would work fine, and it did... until I pinched some wires putting the shell back on. It didn't survive that. Oops...