No matter where you find them unless they are the ones supplied by the original medical device manufacturer, fitting them would constitute a modification!
Unfortunately then I suppose the biomed is dead, anything we fit must be OEM, might as well send all repairs back to OEM, just to be safe. Fitting a new fuse, if not brought from the oem, with associated traceability, would constitute a modification, CME don't want the pumps used with any but their "recommended" PP3 batteries, so a district nurse fitting a battery she bought from the local shop is modifying the device.
Maybe we should just stop doing anything and let the OEM control the whole process.
Sorry MikeX but the level of defeatism is not how change has been brought about in industries that monopolise and control publicly funded bodies, where they see us as a cash cow.