The Star Wars universe is diverse and has a lot of lore surrounding the Mandalorian culture. The Mandalorians were a clan-based cultural group that was composed of members from multiple species all bound by a common creed, language and code. They originated on the desert planet of Mandalore in the galaxy's Outer Rim Territories and had a particularly important role in galactic history as legendary warriors against the Jedi.
In terms of costuming for Mandalorians, you can customize them almost however you want and it would still be canon and fit in with the rest of the universe. Many people make their own custom kits and join costuming clubs like the 501st Legion or the Mandalorian Mercenaries Costuming Club. They do charity work, troop in parades, and sometimes even appear in Star Wars films/TV shows when their costuming departments don't have enough costumes of their own.
Here are a few kits I've worked on for myself and some other clients:
This is my personal Din Djarin inspired kit.
Here is a custom kit that is a mashup of a Mandalorian pilot and Iden Versio of the Inferno Squad.
Other various kits, armors, and helmets I've contributed to.
