If you need parts such as a new battery or grinding wheel guard, or are in need of new parts begin your own repair, see the links below for the RYOBI parts list and there numerical codes. The first link provides a parts list for your grinder. The second is the link leads to the ordering site provided by RYOBI.
[https://manuals.ttigroupna.com/system/files/7695/original/P421_190_r.pdf?2013|RYOBI 18V Angle Grinder Repair Sheet w/ Parts]
[https://www.ryobitools.com/power-tools/support/parts|Click on link for POWER TOOLS PARTS on this page]