Zbbcat2.. hi love chaste - vitex trees. I have had one for over 20 years thru snow , ice and drought summers. And moved three times. Once established they are very hardy tough shrubs / trees. I treat mine as a small shrub 7-8' keep in protected area from high winds. It's also used to make medication to treat "Cushing disease". The tree has lovely bright blue blooms in summer in my zone. It's a under used under story tree in landscapes and has a easy care growth habit once established.
To find a chaste tree ... contact a nursery in your area , ask if they will order one for you. Many will do special orders . If your interested and a friend who currently has one, a tree can be grown from the existing tree. Limbs from current growth can be rooted from side branch by placing stem under soil still attached to the tree . This is the perfect time of year to start new growth from stems. New wood that has hardened off is a good candidate. By removing 3-4 leaves this will leave nodes on the stem where roots will form under soil . Also dip in willow water . Willow branches soaked in water over night generates a hormone to encourage root growth. Place a rock over the stem area to hold down the small branch in place still attached to the tree. Monitor the stem thru the rooting period, keep damp not wet never allow the area to dry out. Adding plastic or moss over the area will help keep the area from drying out and protect from harsh weather over winter.
It's best to take 3-4 small new growth woody branches to have a better average for rooting stems from the main plant.
By spring cut the stem from the tree, roots will have formed enough from the main branch, then plant in new prepared hole .
Good Luck 🍀
