I spent a week making this, at least five days of which were solid work. I did the best research I could on the shape and features of the plush, given that I don't have one myself to refer to (want to thank me for making this? hint-hint). Unfortunately I had to do some ugly warping on the back to get it to fit the head properly, and I didn't have the internal mask base from which to size it, so you will sadly see through the model from behind... but on your character it will look just dandy. An auto-update feature has been included in case I ever make improvements to the mask (and there are some to make), but I'm not making any promises as this project almost killed me as it is. Please note that this mask has no native support for customisation - that's a whole other kettle of fish I don't want to get into.
Installation: Export the folder from the .zip into PAYDAY 2/assets/mod_overrides, and you will find your new mask in a new "Mods" tab when you go to buy it. This mod requires BeardLib and BLT (or SuperBLT, if you have it).
Credit to the creators of the Fate series, and that absolute madman who made the original auction/meme. Also thanks to @AJValentine for his mask template, which helped me through this troubled time. This meme may be dead in a few weeks, but it will live on forever in my heart.
For other lovers of this gay bean, don't forget to check out Haunted LootTags, which turns loot bags into this adorable fella.