I have never played this game, so I am not sure if this will resolve your issue:
If you were storing your items in a database, you would use php to execute a MySql command and bring back the random 100 results
You can google "SQL Select Random" and "SQL Select LIMIT" and you will find some good information on how to write a MySql command that will bring back random results, and limit your result count to 100.
Best of luck