There is this Memrise work booklet with some phrases and words, the author pitched it as something an Inner might use to pick up some belter words.
Our beratnas over in r/LangBelta are also a group dedicated to learning some parts of the Belter Creole, so they will also have good resources.
Oye! I teach immersive Lang Belta at conventions, and I'm half the team that made a Memrise course on it - it'll get you started, and then you can keep going! r/LangBelta is good, and there's actually quite a bit of discussion on Twitter as well. https://www.memrise.com/course/1476694/lang-belta-belter-creole-phrasebook/
I bought 2 stickers off Amazon of that image for my motorcycle.