Available now, authorized by worldofjani.com is this 1541 Diagnostic cartridge for the Commodore 64 or 128 in 64 mode.

This new version 4 includes a built in reset button as well.

This is a gold plated cartridge.  Unlike the boards with the "tin" style cartridge edges, this version won't damage your cartridge port by wearing and clogging your port.  Further, it is designed to fit in a standard cartridge shell that supports a center screw.

This cartridge also features a solid color power surface mounted LED (indicating that your computer is supplying voltage on the 5V line).

Works on all Commodore 64 and 128 Models (in 64 mode). 

This is the Cartridge you'll need if your interested in putting your 1541 through it's paces as you work on restoring it to it's former glory.

Works on both NTSC and PAL computers.

For details on use, please visit the worldofjani website.