Kitchen cabinet shelf support pegs mystery

Hi folks! Recently we put something too heavy on a kitchen cabinet shelf, and two of the support pegs failed and sheared off. Problem number one is going to be getting the broken piece out from inside the hole on the cabinet wall -- it's broken off flush with the surface! Any tricks for that?

Second, and more mysterious -- perusing places like Home Depot, it seems like support pegs are usually pretty standard. But I can't find any that fit our cabinet! The design of the peg is unusual, it has ridged pegs and doesn't seem to be a normal size. Unfortunately these were installed by a previous owner of the house.

I took pictures of one of the pegs from different sides. One pic is attached with this message, but all three pics can be seen here: https://www.screencast.com/t/E25DR2a2B8l. If it looks at all familiar to you and you have any leads, please let me know! Many thanks!