There are also some self printing options out there:
https://www.onlinelabels.com/materials/polyester-laser-labels
I've been using these (the clear matte laser version) to ID all sorts of equipment for my business and I've been using them on some of my dive gear as well. Applied dry and clean they last a good long time even with water exposure. I wouldn't count on them to last forever underwater but I just stick a couple on any single item and replace as needed. I can also usually find a place to put them that is dry but easily found and sticking them in the battery compartments and on the batteries gives a 'last resort' guarantee that one of them will survive and be looked at by anyone that finds it. They are dirt cheap and I just print whatever info I need on them.
Then, for Ptouch (Dymo/Brother/Rhino/etc.) type labels - there are various types including 'extra strength adhesive' versions. I haven't tried them underwater, but they do hold up against rain. Similarly, relatively cheap and replaceable. You can get Brother label printers for nearly free if you look around and one tape cartridge will last you a very long time if just tagging dive gear.
With all of the above the trick is applying it clean (no finger oils) and dry as well as giving it a good rub into the surface if there is any texture present.
Another thing I'm just in the process of trying is some custom 'ID' cards using Vistaprint's plastic business cards. They are an international supplier of web order printed material and I've used them for regular business cards in the past - the option I'm using will give me something essentially equivalent to a standard credit card/ID sized plastic card but printed with my own custom information including contact info, emergency contact info, insurance info (providers, accounts, phone numbers) and a QR code / URL that I can publish travel itineraries and anything else I might want to add in the future. I do most of my travelling alone and it seemed prudent to compile all the 'if you find my body' info in one place. However, these will also be good to attach or put inside various pieces of gear and should be quite durable. Will see how they turn out in a few days...
(Note: if you use Vistaprint there is always a coupon code out there. Usually 30-40%.)
Anyways... a few cheap/non-standard options I've been experimenting with. Certainly $25 for a sheet from that dive labels place is not a terrible deal if you only need one sheet.