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We have lots of gall wasps and the only ones I've seen are a light brown. Great idea, it's kinda similar. These are perfectly round, too, which is not what I commonly see here.

Gall wasps produce a wide variety of gall shapes and colours dependent on species. This link is to a wasp that produces a very similar colour and shape: http://www.naturespot.org.uk/species/smooth-pea-gall-wasp

That's definitely it, mystery solved. Thank you!

I searched a little further and the inside looks like a wasp gall for sure. I've been a nature wanderer here my whole life and have never seen this type. Thanks for the idea, I'll keep my eye on them.