Probably what you'll need to use is the Parametric Bootstrap Cross-fitting Method. There is a good description of it in this answer: measures-of-model-complexity Here is the reference:
- Wagonmakers, E.J., Ratcliff, R., Gomez, P., & Iverson, G.J. (2004). Assessing model mimicry using the parametric bootstrap, Journal of Mathematical Psychology, 48, pp. 28-50. (pdf)