Liquid baking chocolate is very simple stuff that you can easily make yourself.

What makes chocolate solidify is cocoa butter, a fat that is solid at room temperature. Baking chocolate is about half cocoa butter, the other half is cocoa solids, the same thing as cocoa powder. Liquid baking chocolate is just a mixture of cocoa powder with an oil that won't solidify at room temp.

To make your own, use unsweetened cocoa powder (most big grocery stores carry this) and any bland oil (e.g. canola oil). For the equivalent of 1 oz. of baking chocolate, stir together 3T of cocoa powder and just enough oil to liquify it (start with 1T and add more if necessary). Ths stuff will keep for months well sealed and in the fridge, so you could make a larger batch for future use.