Are there any recommendations?
Has anybody reached out to NXP for a distributor?
I have bought mine here: 25 x Original NXP iCode SLIX-L 13,56MHz RFID Tag (ISO 15693) Klebesticker | eBay
sadly they are sold out. Maybe you can contact the seller and ask if he is expecting to get some more. They do work as I expect them to work, so I think you can buy there if he has some again.
On his website he says “lieferbar ab 15.02.”
https://shop.electricky.de/RFID/Original-NXP-iCode-SLIX-L-13-56MHz-RFID-Tag-ISO-15693-als-durchsichtiger-Klebesticker-32mm.html
Thats the same name as the ebay seller. Good to know he has a shop and restocks 
Can confirm accuracy in product from this vendor.
I bought also those Tags via eBay. Works as promised.
Tag ID starts with E0:04:03
From almost the beginning of our journey, RFIDfriend helped us out with the correct NFC tags. He was the one that took the fight / discussions with Chinese suppliers to get his hands on the correct version of chips.
You can find him on Kleinanzeigen, via eMail (RFIDfriend@gmail.com) or directly within Telegram at #RFIDfriend. Just look out for the RFIDfriend name.
You can find him on http://www.rfidfriend.com as well.