I liked Mrcleanr6's razor blade scraper for getting under prints on the bed, but my 22mm x 43mm double edged razor blades were too wide and weren't centered in the holder, so I redrew it to fit. While I was at it, I added a slip cover because I am leery of leaving exposed razor blades lying around.
There is a new version with blade locking available.
Or try my latest model with superior blade retention.
Designed for 0.15mm layer height, 0.40mm extrusion width. Other settings will probably work, but small dimensions will be off. Print cover sideways or slot down. Print without supports.
There is a single 0.40mm wide track on the insertion side of the holder, to give the top layer of the slot something to bridge to and keep the slot fairly clean. You must break through that before inserting a blade from the side. Printing at higher than 0.40mm will not lay down that bridging point, but it will still work, as in the original version.
DesignSpark Mechanical CAD file is available.