Its in the redwood , enter at the rivermouth from the snow biome, follow the river to were it 1st forks keep flying straight over a small bump/hill, there will be a raised cliff/hill infront with a small cave opening ,,,, you have reached your location, if that doesnt help let me know and will get you exact cords.

18.4, 21.6 thats the entry. I was getting coords inside the cave

i found it shortly after posting this.... still trying to find some others... found a cool little volcano cave though!