They spawn at random chances on all maps. So there is no such guaranteed places to farm them. You just have to farm in any mission except the very first mission (I haven't seen them in that map) called Aogiri Tree Hideout. Also avoid farming them in Disposal Facility because that map is very hard to farm alone, although there exists a chance to get Kisho Arima. 

If you need Kishou Arima, play as Ghoul on hard campaign.
If you need Centepede Kaneki, play as CCG on hard campaign.

Additional

NOTICE: This guide will only give you Quinque Shards not Chunks, and you may not always be given the shards first go. You can also gain them through PvP!
Looking for how to defeat Kishou Arima easy? Click this link: https://www.animeesports.com/showthread.php?tid=891

[Video: http://https://www.youtube.com/watch?v=D07MrvkPyhw]

When you play ghoul or premade anime characters, just press only dash button, then your character will backflip. 
This backflip has 100% chance to evade all incoming attacks.

Unfortunately, all custom CCG characters can't use it, but premade anime characters like Haise can do it.

Also, there is a small chance to be immune to special move's stun effect, you just use skill at the same time your enemy performs special move.

Also, getting into awakening mode will provide you immunity against such

Takes 30 seconds if you ignore all enemies and just run to the area. Its the only map that's the quickest however not ideal for getting shards and chunks. I also put in some tips when facing him!

More Arima guides:

Defeat CCG Reaper easily

[b][url=https://www.animeesports.com/Thread-How-to-easily-get-Kishou-Arima-Quinque-Shards-UPDATED--911]Kishou Arima -Quinque Sha