Welcome to Photrio. That leak looks like it's located at the bottom of the shiny roller. You may want to get some self adhesive felt or foam and experiment on covering that area.
Unfortunately most repairers don't do a film test for light leaks, but light seals are simple enough to replace yourself.
An alternative that would probably solve your particular case is adding some kind of leather half-case to the camera, either old or newly manufactured... the old ones have two halves that can be separated and you can just use the bottom.
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