Looks like @jamiek included a LR3-strut-plate-variable_900x6.svg that’s pretty close to 3’, see Printables , think the set of struts he uploaded are generated using his OpenScad based script that can be used to make any strut length you’d like.
Also, @tgm022861 made parametric Fusion version at Fusion 360 Parametric Model for Strut
Both options look cool, haven’t tried out either yet, still wiring…