CryptoKeys - https://crypto-keys.com/ - a durable and simple solution. The manufacturer offers "classic" recording boards with lines, but it is better known for its appearance-specific "keys". This is a series of numbered stainless steel plates threaded on a metal ring. Seed can be stamped out, or you can order ready-made labels in a shuffled order and sort them yourself. The manufacturer declares a temperature resistance of 2000 ° F (less than 1100 ° C) for 10 minutes without damage and a pressure resistance of up to 20 tons.
Another affordable steel wallet you can look into are crypto keys.