I sometimes play with a fellow who has small hands. He plays a Bach Strad trumpet with first and third valve triggers, special ordered from the factory.
I have an old Selmer trumpet with a factory first-valve trigger and a third-valve trigger that was obviously added later. The workmanship on the third trigger is a bit rough, but it works well and is operated by a lever that's very close to the third valve casing. I can imagine this layout would be very usable for someone with small hands. Here's a pic:
