There is an IBIS model available for the AD7091R MSOP package that can be downloaded at the following link:
http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7091r/products/tools-software-simulation-models/index.html
The characteristics for the MSOP package and the LFCSP package should be similar so it is recommended to use this model in simulations for the LFCSP package.