You could get in-line "interrupter" brake levers.
but given your hand size, it might just be worth your while to get a more recent-design brake lever. and they even make them for smaller hands (shorter-reach levers). My recommendation would be the Tektro R341.
These will likely make a big difference compared to 1980s levers.
If you want to also have brake access on the bar tops, you could go for interrupter levers, but you don't need to start there.