A dry herb portable vape?
Grasshopper gets tops marks for discretion but more of a one or two hitter than a session vape.
I recently bought a Minivap (from Hermes Medical in Spain). It's portable in that it can run off a battery (as well as mains), but not discrete (about the size of a can of Red Bull). I use it exclusively at home through a glass water tool for long (15 min) sessions. The flavor with this one is immense.
I also have a Mighty (from Storz & Bickel of Volcano fame), which is also a decent device. Used to have a Magic Flight Launch Box but didn't provide enough extraction for my needs.
Plenty to choose from, so decide whether you want a conduction or convection (or a hybrid) vaporizer and that will narrow your search somewhat.
Spending $40 on a junk pen you'll throw away after two uses is a complete waste, imo.