Although few band compositions include parts for E flat contralto and B flat contrabass clarinets, directors can readily adapt parts written for other instruments. Blaufuss offers suggestions on how to score parts for contra clarinets.
Blaufuss, Dan (2006) Scoring Parts for Contra Clarinets. In: The Instrumentalist, Vol. 60, No. 9, pp. 44-46. Available at https://openmusiclibrary.org/article/453928/.