need to find out if there is a machine out there used to claen large
commercial buildings floor mats approximatly 5x4 in size or so.

take them to a drive thru help-yourself car wash and bring a scrubber
there are also services that come and swap weekly

An alternative is to use a professional mat rental service. Let them
come in and clean and replace them on a regular basis. When they
become worn out, they replace them. One such company here is St. Louis
Mat Company. You might enquire with them about pricing and such.

http://www.stlmat.com/