Reddit mentions of Guerrilla Tees Dungeons and Dragons yin yang Shirt Good and Evil DND Tshirts, Grey, Medium

I don't know how he is about clothing, but a shirt he might find amusing: https://www.amazon.com/dp/B014FRG5TI

D&D Animated Series: https://www.amazon.com/Dungeons-Dragons-Complete-Willie-Aames/dp/B002DH20Q0

Another Shirt: https://www.amazon.com/Dungeons-dragons-shirt-tshirts-Medium/dp/B01BFXDZMK

A container for his Dice or cards: https://www.amazon.com/LOOMEN-Treasure-Chest-Gaming-Container/dp/B01K5JPTWE

D&D Movie Collection: https://www.amazon.com/Dungeons-Dragons-2-Movie-Collection-Blu-ray/dp/B004DN2Y5O

A cool book about creating makes for D&D, we have this and it's interesting and not too difficult with the instructions: https://www.amazon.com/How-Draw-Fantasy-Art-Maps/dp/1440340242

A dorky mug: https://www.amazon.com/Critical-Hit-D20-Ceramic-Mug/dp/B017V0MMIE

A thing for his dice: https://www.amazon.com/Dungeons-Dragons-Mimic-Gamer-Pouch/dp/B01DN2B10E

A cool colouring book for adults: https://www.amazon.com/Cthulhus-Coloring-Necronomicon-Sunny-Doings/dp/0692390561

I'm sure he has a set of dice, but if he doesn't they have tons of those for cheap on Amazon, in all sorts of colours.

This is a PS4 game, it's an RPG type, which seems like what he might be into: https://www.amazon.com/ArcaniA-Complete-Tale-PlayStation-4-Standard/dp/B00TKLFOKQ

ANother PS4 game: https://www.amazon.com/Dragon-Quest-Heroes-World-Trees-Blight/dp/B00TUFUD0S

For Magic, they have random sets on Amazon for cheap, with "rare" cards, I don't know if he needs more cards and what not. https://www.amazon.com/Random-Cards-Foils-Mythics-Planeswalkers/dp/B00HECBR9K

Here is 1000 random cards to boost his collection: https://www.amazon.com/Magic-Gathering-Cards-Rares-Mythic/dp/B007G91FZ2

Little figures, from the Magic game: https://www.amazon.com/Funko-Pop-Games-Gathering-Beleren/dp/B00J227MF8

https://www.amazon.com/Funko-Pop-Games-Gathering-Wildspeaker/dp/B00J227LSQ

https://www.amazon.com/Funko-POP-Games-Gathering-Figure/dp/B00MWUYQ10

https://www.amazon.com/Funko-POP-Games-Gathering-Tezzeret/dp/B00MWUYPMA

Let me know if any of these seem like good ideas, or something is close and you need more along those lines, this was just a few minutes of searching.