Need suggestions about smectite or other High plastic engineering material?

I am looking for Smectite or any engineering material that I can use in my soil to measure the plastic limit. I have a dataset of 150 samples with max plastic limit 31% and I want to increase the variability of my dataset (plastic limits with 40 to 50 %) and need any suggestions from where I can get high plastic soil samples or any engineering material such as smectite to add in my available soil and can measure plastic limit. suggestions will be appreciated a lot.

Soil Mechanics / Geotechnical Research Geotechnical Investigations & In-Situ Testing