Where can I order Harlequin in a vape cartridge?

Most of the people that I have talked with that have tried Harlequin have been from the San Francisco area, So your best bet would be to try contacting a delivery service in San Francisco and ask them to find it for you. I wish I could be of more help but this might at least get you started on your quest in the right direction. The people I have talked with that use Harlequin do love it, so I do think it's worth hunting down.