Final Fantasy XV A Better Absorb Shield is a side-quest you can complete by talking to Cid in Hammerhead and Tony in Cape Caem.
This can be done after you complete Living off the Land side-quest for Iris, who will teach Noctis how to plant and harvest these specific vegetables.
Once you complete the said quest, Tony will spawn in Cape Caem and if you agree to trade Caem Carrots for weapons, he will eventually give you an Absorb Shield.
So, first finish Living off the Land, then plant more Caem Carrots, and rest for one night.
In the morning, harvest the carrots, talk to Tony and trade them for a weapon. The weapon you receive is random; therefore, keep trading until you get an Absorb Shield.
Objective: Find a Spiked Armor for Cid
If you show Cid the Absorb Shield you just found, he will immediately agree to upgrade it for you and turn it into an Absorb Shield II, but only if you find a Spiked Armor.
Be advised though that it is a level 38 hunt, and it can be difficult to complete without proper spells or weapons.
Travel to the marked area on your map while tracking the Hammer the Cannibals quest, and when you get close to your targets, equip a shield.
Use Ignis’ Enhancement skill to imbue your weapon with ice, and stay behind your enemies all the time.
There is a 75% chance for a Skarnbulette to drop a Spiked Armor, so by the time you finish the hunt, you should have more than one material required by Cid.
Objective: Give the Spiked Armor to Cid
Go back to the Cauthess Rest Area outpost to retrieve your rewards for finishing Hammer the Cannibals hunt, then travel to Cid and hand over the Spiked Armor.
Assuming that this is the only active quest you have started from Cindy’s grandfather, he will begin working on your upgrade immediately.
To speed up the upgrading process, focus on finishing one hunt or one side-quest, then rest for one night. In the morning, Cid will call Noctis and inform him that the Absorb Shield has been upgraded.
A Better Absorb Shield Quest Info
Description: “A master mechanic, Cid can modify mechanized weapons to unleash their full potential. If Noctis can obtain a hide of spiked armor, Cid will upgrade the Absorb Shield – but he might take a while.”
Reward: Absorb Shield II x 1
Post Quest Suggestion
Complete A Better Pair of Plunderers side-quest.