"Many brands of breaker panels can accommodate half-sized double pole
breakers. " " was built in 1990, so they aren't THAT new"

We built our house almost 40 years ago and used some of these duplex
breakers then, they came from Sears, I think they are square D.

"the double half sized breaker would need to come in contact with both poles
"

Switch a couple of 110 circuits onto a duplex breaker, use the vacated space
for the 220v.

Walt Conner