I can’t think of a website that matches words with their slang equivalent.
However, maybe you can do something with this by wandering…
Type any word on the search bar on the top right, and then you can go for a random word. Maybe you’ll stumble upon one you can use

https://www.dictionnairedelazone.fr/

EDIT :
Even better, go directly here in the website :
https://www.dictionnairedelazone.fr/glossary/lexical

so you can pick a word you’re interested in and see if it has a slang equivalent. You can even get real examples of usage (mostly in french rap songs)