Where do you get max repel from on Pokemon diamond?

You can't get Max Repel in Pokémon Diamond. The only Repel types in Pokémon Diamond are:

* Repel: Prevents encounters with wild Pokémon for a short time.

* Super Repel: Prevents encounters with wild Pokémon for a longer time.

Max Repel was introduced in later games (Pokémon Black and White).