spearmint is a tough one, since there is always the propensity it will taste like toothpaste.
I got some from Vapewild that is pretty good.
decadentvapours has a wonderful pre mixed spearmint
ejuice but you have to shop in the UK site to get it (worth it esp for their great coffee vapes too!). Vape Dudes was pretty good, less sweet if you like that. They have a vanilla mint that is very good....ITC has a Wintermint that is combo wintergreen + spearmint + menthol.
Also a winner is Copper Creek creme de menthe though not really spearmint per se. Ditto Plume Room Creamy mint, fantastic vape.
I hate menthol anything, so I need pure mint.
I would stay away from the MTB and Virgin Vapors ones IMHO.