Hey, just wondering if the magic items in Volo's Guide, such as Mind Lash and Shield of Far Sight appear as magic items to be added to character inventory? And if not, why not? They're magical items in the book and I've already bought the book so I thought I could have added to my PC's inventory when they found them

As those items can only be used by Mindflayers, they are not available for player characters:

Mind flayers craft magic items that only they or their thralls can use — a sensible security measure to keep enemies from turning the illithids’ own creations against them.

One of my players has willing become a thrall to an Illithid in my Campaign for access to stuff like this. 

Quote from Elessar106 >>

One of my players has willing become a thrall to an Illithid in my Campaign for access to stuff like this. 

 Doesn't becoming a Illithid thrall remove a free will from the victim as well as requiring a mind flayer colony to work (I assumed this because creating a thrall affects the whole colony)? Therefore, if your player did this they could no longer control their player.

Quote from RAM3 >>

Quote from Elessar106 >>

One of my players has willing become a thrall to an Illithid in my Campaign for access to stuff like this. 

 Doesn't becoming a Illithid thrall remove a free will from the victim as well as requiring a mind flayer colony to work (I assumed this because creating a thrall affects the whole colony)? Therefore, if your player did this they could no longer control their player.

 Unfortunately the campaign had to end because of time constraints but the PC was an active spy for a Mind Flayer that was looking for a new area to create a colony of their own. I allowed them free reign to RP as they would, the Player made these choices to become a spy and thrall, and every now and again they were given direct instructions to follow.

Quote from Stormknight >>

You're welcome to use the information available to create homebrew magic items for your campaign, but unless full information is provided, we can't add them to D&D Beyond. This includes item rarity and the item type.

I've since made them in homebrew, I didn't have much experience with the making homebrew content on DnDbeyond at the time so I was worried about messing it up.

Thanks for the replies everyone

Quote from MellieDM >>

As those items can only be used by Mindflayers, they are not available for player characters:

Mind flayers craft magic items that only they or their thralls can use — a sensible security measure to keep enemies from turning the illithids’ own creations against them.

rouge lv 18 thief

Does this mean, that the Mind Lash (official item from Volo's Guide) won't be available to be added to the players' inventory?

But that's my problem, that it does not show up in the search, when I try to give it to a character from the character sheet.

Quote from Dertian >>

But that's my problem, that it does not show up in the search, when I try to give it to a character from the character sheet.

 Does the owner of that character own Volo's Guide to Monsters, or have it being shared to them in the campaign they are a character inside of?

The character is in a campaign, that has every source shared by me. It uses many parts from other sources, and I even could add a Mind Blade to him, that's similar to the Mind Lash.