Just a heads up for anyone looking to make tonic water and wants a local source for cinchona tree bark. Sure, powder is easily available online, but I like to have local options available, and googling didn't turn anything up for me in SF.
I was looking through the packets of spices at Duc Loi market in the mission, and noticed a packet of if it, labelled quina. .37oz is 99 cents, so about the same price as I saw mentioned on the boards here about a store in Berkeley. I've seen it at a number of of markets around the mission-ones that have a very large variety of spice packets. Mamå brand, with a brown label, is the one I've found with this stuff.
It's pretty chunky, so I use my large stone mortar to break it up without powdering it. Recipes for tonic water are easily found online. It seems that the powder is tricky to filter, so this works out nicely.
It's gratifying to be able to make a good tonic water. I love the Fever Tree brand, but it's hard to justify $6 for a four pack of wee bottles. The only thing with the homemade stuff is that it's not clear, but that's fine for me.
Hope someone out there finds this useful.