Leather scent is VERY difficult to replicate. I have been through all the noxious imitations as well.
There is a company near me that makes custom 100% natural air fresheners and they have leather as one of the scents. I have used it and it makes your car with leather interior smell like brand new again. It is awesome stuff. They are hand made and can be ordered in almost any color. They are scent beads that come in a draw string sachet sack that you can hang if you wish but I just usually throw it in the glove compartment and it lasts for at least 2 months...NO KIDDING

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PM me if you would like to contact the maker, they also have 90 other scents that are all very popular and 100% natural.