Iris has merged in a proper shaderpack selection menu. I suggest recompiling Iris and switching to it!
A resourcepack-screen solution for shaderpack selection in the Iris mod compatible with Sodium.
This mod depends on Iris!
To be able to use this mod with Sodium, you'll need to compile the compatibility branch of Iris for Sodium and the Sodium fork by IrisShaders.
Just clone or download the source code on github and run ./gradlew build inside their project. The Sodium fork by IrisShaders requires the Iris.jar in the project folder /build/loom-cache, so make sure to compile Iris first and move/copy the jar to that path.