There are hand stretching exercises and an effective device.You can find easy by google increase handspan.
How far a person can reach is based on finger length and hand width. A person with short fingers and big hands can often reach further than a person with long fingers and small hands, for example.
A simple method of increasing reach, something I've been doing for years (I have relatively short fingers and medium sized hands) is by grabbing my leg (left hand, left leg), then taking the thumb and slowly pulling it up and in while leaving the rest of the fingers on the leg.
You'll notice right away when you're doing it right because you'll feel a stretch that goes from the base of your thumb to the base of your little finger, right across your hand.
Don't do it to the point of pain, just to the point of stretching.
If I do this before a solo gig, I have an extra half inch of reach (and the benefit of stretching out my hand!)
I'll also use this technique on my other fingers, but much more delicately since they don't really want to stretch like this.
Remember all these stretches must be done without damaging yourself. Start slowly, start easy, and as time goes on you'll benefit greatly from it.
Volume 1 of this educational jazz piano book contains 15 jazz piano exercises, tricks, and other interesting jazz piano techniques, voicings, grooves, and ideas Scot Ranney enjoys playing.
Volume 2 has 14 jazz piano exercises and tricks of the trade, and quite a bit of it is Calypso jazz piano related material, including some Monty Alexander and Michel Camilo style grooves. Jazz piano education is through the ears, but books like this can help.
Volume 3 contains 12 jazz piano exercises and explorations by the acclaimed jazz piano educator, pianist, author, and recording artist Tim Richards.
Volume 4 is by Jeff Brent, a jazz pianist, composer, teacher, and author of "Modalogy" and other acclaimed jazz theory and education books. In this book Jeff shares detailed analysis of transcriptions of live performances. He covers everything from the shape of the songs to the tricks and licks he uses in improvised lines to the ideas behind his lush chord voicings.
One Hour of Relaxing Piano Music
Jeff Brent's Jazz Piano Notebook
Fundamentos Físicos del Sonido
Aprendiendo a tocar PIANO gratis con partitura
5 Pro Tips for Practicing Jazz Piano
"Danny Boy" Jazz Leadsheet