To add to Armin's response, we cannot provide any access to the source code. The latest registered changes in the MAT_197 code were:
"New option for sliding isolator with rim failure (TYPE = 5)."
"Added better error trap for MAT_SEISMIC_ISOLATOR Rate=3 missing input properties."
on March and May 2019 and should be both available in R12.0.0 and later versions.
Let us know if you have any concerns with the behavior of MAT_197.