crazy Modeler Super Abrasive Sanding Sticks are good for me.
Though they are large when dealing with tiny parts,you can cut them into smaller shape.The fine and the finest sticks will not harm your plastic .They are flexible ,soft and washable:-)
http://www.hiroboy.com/catalog/produ...oducts_id=2571
Maybe can try stradasports.com .I guess they are selling CM items,too.Good luck