I’ve not seen 3rd parties offering AppleCare, they tend to push their own insurance products.
If you got a good price on your watch then AppleCare ends up being a considerable on top cost.
AppleCare pricing for watches is the same whether you buy the cheapest 38mm series 1 vs the most expensive series 2 with steel band.
So for me the pricing isn’t worth it if you’ve a cheap watch.
I did however buy AppleCare+ on my 10.5 Pro as the price seemed more reasonable.