Text-based clues can be searched by the first 4 words.

Clue hunter outfit:

Wearing the clue outfit replaces the required items. The pieces can be obtained from hard and elites. The outfit consists of 6 pieces.

Helm of raedwald
Clue hunter cloak/garb/trousers/gloves/boots

Master scroll book:

The Skill points shop sells a Master Scroll book, which will directly teleport you to the clue location. You can do this by going to your current clue location, then use the clue on the book. This will sacrifice the clue, and the location will be saved.

Clue scrolls stack and can be collected indefinitely on RuneRealm. There is a clue shop which sells most of the cosmetics you need for Double Agent clues.

There are also certain custom shops that sell Clue Boxes, which will provide a random clue when opened. The chance of getting a specific clue from clue boxes are as follows:

Easy - 40%, Medium - 33%, Hard - 22%, Elite - 5%