I highly recommend the Sharx by Fox 40. I have four. I also highly recommend the Sonik Blast by Fox 40, which is shorter but fatter.

I don't think either of the whistles you listed fall into the "compact" category, but they're about as small as they can be for their performance.

Note the Safety Whistle you listed has a pea. I prefer pea-less because a pea may freeze up in freezing environments.
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