Hello folks. Not sure if anyone still posts here, but I have some questions about the Link's Treasure Hunt quest. I've currently beaten Level 4 (Desert Temple) and I have the following items in my inventory:

8 heart containers total (haven't found any in the overworld, if there are any to be found)
White Sword
Blue Ring
Blue Candle
Regular Boomerang
Hookshot
Letter/Potions
Raft
Ladder
Whistle
Magic Wand
1st magic Container
Enemy Bait
Sword Slash technique

I've also competed the Hero's Grave, but obviously I can't claim that prize, so...

I've seen at least 4 places in the overworld that seem to require the Super Bomb to access an item or progress in the game, but where do I buy Super Bombs?

Any help would be appreciated. I like this quest so far and would like to complete it. Thanks.