According to the website Solo contains;
Turkish small leaf tobacco is sun-cured then overlaid with a menthol extract derived from genuine peppermint leaves. The result is a fresh, crisp, mellow and ultra-smooth experience.
It seems like you will have to make your own. You can try adding fresh mint leaves to PG and leave that long enough for the mint to permeate the PG.
Then you would have to figure out how much to use.
Peppermint FLV and Mint Medicine Flower are two that’s just FAB and no toothpaste aspect to them IMO. Both are super duper concentrated at 1-2 drop per 30 mls of finished ejuice. I’ve paired both with synth tobacco recipes with very good results.