Are you wanting menthol flavor or e-
juice? If it's flavor, I would suggest making your own. It's cheap and easy. I make a 10ml batch at a time per onestopDIYshop's instructions. It really only consists of pure menthol crystals and PGA. Add as much or as little as you like for menthol flavor. I only add 1 drop per mL to enhance the flavors I'm mixing.
If your looking for menthol e-
juice, someone else will have to chime in. I DIY all my
juice. I have made some potent menthol tobaccos, tho.