I'd use some form of Support class and store the types as an array.
<?php
namespace App\Support
class AgencyType
{
private $types = [
1 => 'type1',
2 => 'type2',
//etc...
];
public function find($id)
{
if( isset($this->types[$id]) ) {
return $this->types[$id];
}
throw new \Exception('Type does not exist');
}
}
Having it a class is more Object Orientated also it does give you the flexibility to update your types in the future (I know you said you don't need to but there is probably a good chance you will in the future).
You can now also add a method for getting all the available types to use in a form etc and it is all managed from one place.