Certified GKH Gardening Expert
You will need to clone the tree. Taking several tip cuttings and rooting them with a rooting compound will ensure that you get at least one rooted tree clone. Many clone attempts will fail, so you will want to take as many as you can in order to make sure you get one tree.
Now, if you want an exact replica of your tree, you will need to find out what the graft stock was (most likely flying dragon trifoliate orange) since this attributes to the size of the tree, the vigorous growth, and a very small portion of taste. Otherwise, just a regular rooted tip cutting will give you an almost exact replica of your tree except for its size. It will likely be much taller since it does not have the dwarfed rootstock.
This article will give you more information on how to properly take cuttings: https://www.gardeningknowhow.com/ornamental/trees/tgen/how-to-root-cuttings-from-various-shrubs-bushes-and-trees.htm