Too small

Update: I fixed it!

I bought some cord locks (aka cord stoppers) online (I tried every local shop that I could think of; nothing). They seemed perfect for my needs, except it turns out that the inner hole is smaller than the outer hole; it was the outer hole’s diameter that was given, and the discrepancy wasn’t obvious. This means they are too small for the cord ends. I am displeased.

There is not one suitable alternative on the internet, so I need to enlarge the inner holes. Ideas, anyone?

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