Honestly, I haven't seen much that purely focuses on Shantae and Bolo as friends, like, in a deep platonic way. Most fics that put them together tend to veer into romance territory pretty quickly, which is fine I guess but misses the point of their actual dynamic in the games.
If you dig around, you might find some older one-shots on FanFiction.net from back when the series was newer, where they're just hanging out in Sequin Land or Bolo's trying (and failing) to impress her while she's just tolerating his nonsense. That felt true to them. Nowadays a lot of the stuff on AO3 tags them as a pairing, so you have to sift through the shippy stuff. I did read a cute gen fic once where Bolo helped Shantae fix her hair ribbon after a fight and they talked about nothing important. It was small, but it felt right.