I have a brownie recipe that calls for couverture chocolate to be used. Unfortunately it is getting difficult (and expensive) to obtain this chocolate.
Is there a way to get the same effect using other ingredients?
You can use compound chocolate (the inexpensive "coating chocolate"). It's what you find used in a lot of cheap store-bought chocolate, and it has very similar melting and viscosity properties to couverture.
You can usually find it in most bulk food stores.
The important property of couverture is its high proportion of cocoa butter and correspondingly high fat content. Compound chocolate normally does not contain any cocoa butter, so it is nowhere near as rich as couverture, but it achieves roughly the same fat content with vegetable fat and will act similar to couverture when melted.
Technically, compound chocolate is not actually chocolate, so the result will be lower quality than if you had used couverture; but if you're pinching pennies, I think that's the way to go.
Couverture chocolate is about 37% cocoa butter, 17% cocoa solids for a total of about 54% cocoa content. A common supermarket brand with the same cocoa content will have less cocoa butter, but for brownies that can be adjusted by varying other fats in the recipe.
I buy fine baking chocolate online and it works out to maybe 10% more than one of the common supermarket brands.