I used to be in love with a product called Sebastian Shape Root Lifter, that jet sprayed volume right where you needed it. But since I purchased it at a professional hair supplier called Delorme, I have never been able to find it again.
I did, however find a similar product made by Kiehl’s called Super Thick Volumizer. It’s got the same pointed fire shot thingy to send the product straight to the roots and nowhere else and is great for adding volume around the crown of your head.

Just a note: Plan on washing your hair the next day with this product, because greasy residue is an unfortunate day-later side effect.