I did a lot of grinding over time, so I don't know. I am playing the version here on itch, so it is attainable. Many of the items that weren't obvious came from the tent store at night. Its stock seemed to refresh more than the others. The Silver I got from the Cave by grinding Explore/Escape and I knew that Gold fuses with Silver Items, so I upgraded all of the basic Silver Items into Gold. I got the Silver as the very last thing and wondered how to make silver items and just tried the tresure chest and it combined, but not sure if I could have combined with the lucky cat or another miscellaneous item.