Interestingly enough, iFixit sells the adhesive you're looking for, but only in the Fix Kit version of the battery replacement set.
[product|IF494-003-2|iPhone 16 Pro Max Battery]
If that seems a bit pricey to you, you can also find just the adhesive at various sites around the internet; I usually start with places like eBay, Amazon and AliExpress, myself. Here are a couple of examples.
[link|https://www.aliexpress.us/item/3256807705715753.html|Original 3pcs Back Cover Battery Cover Adhesive Tape Glue Replacement for iPhone 16 Pro Max 15 14 Plus Back Battery Glue Sticker - AliExpress 202192403]
[link|https://www.ebay.com/itm/235935116529|Back Glass Adhesive for Apple iPhone 16 Pro Max Sticky Tape Repair Replace - eBay]