I need to know how to get the 50 Arrows upgrade on Zelda: Ocarina of Time on the VC! I got 40 Arrows. But I can't seem to get 50. I tried the shops. But it says: "You can't get this now".

You get the Biggest Quiver from the horseback shooting range at the Gerudo Fortress, not from a shop. you have to rack up 1500 points, which is a beast and a half, as i recall.

I think what's happening is that the shops have arrows available in packs of 50, but if your bag/quiver/whatever is already full, they'll refuse to sell to you. If you only had like 39 arrows, they'd sell you more no problem, but since you probably already have 40 when you're trying to buy more thinking it's a quiver upgrade, they're refusing and you think they're just not selling the upgrade. :3