The SAM4s ER-925 parts are available here for the DIY repair person. If you would rather have us perform the repairs that can be arranged, however most minor repairs are pretty easy to do in the field by the end-user.
If you can't locate the part you need give us a call and we will see if it can be ordered from the factory. If making your own repairs be sure to unplug the cash register before attempting repairs but only after you have made a back up of the program.