If the foundry could provide this model for you, pls turn for help to the foundry.
But it's not always possible to obtain this model because it's not widely used as normal MOSFET.
When we were doing research on designing Floating Gate Memory Circuitry, we fail to obtain the model from SMIC or GSMC, so we constructed our own large signal model(no need for small signal model of floating gate MOSFET for memory design), even though coarsely, to simulate the Programming, Soft-Programming and Erasing Effect. If the foundry fail to support you, I suggest you do like us.
I hope it's helpful.