Recently came to hear about Gondharaj lemons which is famous for its aroma and is native to west bengal. It is said to be king of aroma, please see the link https://www.thebetterindia.com/186253/gondhoraj-lebu-bengal-fragrance-king-of-lemons-food-india/.
Couldn't find it in any nurseries of Kerala, and finally contacted a friend in Calcutta and he sent me 4 plants through courier. It took 7 days to reach the plants, but they had packed it nice, and hence all plants reached safely. It looks like, it came by air cargo. Planted one at home, by taking 1feetx1feetx1feet pit and filling it with home made compost.