I have two different pair of commerically made climbing sticks. Both are good but since I bought them I have seen better.
One of them I' ve seen but not tried is one made by Reaper (?). It looks like an extending pole of square tubing. You , after extending it, attach the steps without tools. It also has a saw attachment for the end to trim high branhes.
If you have some good sporting goods stores around go in and check out what they have. If you can take them out of the package and see how the carry, assemble and secure to the tree. For some of the units you can purchase extention pieces to reach heights from 12 to 18 feet or more.
Good luck.