Where can I find lots of Eldin Ore and Ornamental Skulls in The Legend of Zelda: Skyward Sword?

I’m at the end of the game, right before you go battle Demise, and I want to get enough treasure for all the upgrades I’ll want to do in Hero Mode, and I need 6 more pieces of Eldin Ore, as well as 6 more Ornamental Skulls. For the Eldin Ore, I’ve dug in every hole I can find, and even tried dowsing for treasure (but i only find amber relics , but I can’t find any. I’ve also run out of gossip stones to give it to me. Where can I get six more pieces at least? And as far as ornamental skulls go, I’ve heard you get them from killing Bokoblins, but I’m just not seeing them. Is there any particular region that has a high probability of giving me them? Thanks.