Inter-Symbol Interference (ISI) channels
Things like the good ole' GSM standard specify power delay profiles and a phase variation model. So, there you go, reference model delivered in the shape of a standard.

Other than that, if you're just looking for any ISI-inducing (i.e. frequency-selective) channel, why not use your favourite DSP framework to come up with a random FIR filter?

Also, a lot of frameworks do come with their own channel simulations; GNU Radio for example brings multiple channel models of varying realism in its gr-channel module.

I often find that students overestimate the complexity of actually measuring a channel impulse response to use it in their own channel simulations. Just send a PN, receive it at the same time, and use a correlation to find the impulse response; if your receiver and transmitter exhibit a frequency offset, you might need to try a couple of frequency shifts and use the one that gives the highest correlation coefficients.