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Hey, thanks for reaching out again!
You are right, there are not many ways to get thorns on gear as of now.
The only way to get thorns on high level gear is to roll thorns on Shield/Armor or pants, there's also a unique shield which grants a lot of thorns. But there are no enchants or something like that for thorns.
I have some ideas in mind which will replace the current enhancement system because it's quite boring just adding armor/damage to all items. The new system would allow you to enhance gear specifically for your character in this case you'd be able to add thorns to most gear.
This new system will take some time to implement since it's paired with loads of other new content.
In other words, you will have to wait a bit before you can play a full thorns character in the end game..