Not sure which generation you’re looking for but these seem to be available for multiple generations of C class, I got them for my W205 and they have been fantastic.

TMB Motorsports All Weather Floor Mats for Mercedes C Class 2015 - Present https://www.amazon.com/dp/B07DHBDQLP/ref=cm_sw_r_cp_api_i_Mz22DbAR9K547