How do you get an oran berries in Pokemon shiny gold?

If you're playing a beta in which the fruit-bearing trees do not appear (like I am), there are three Oran Berries you can obtain:

1. The Oran Berry attached to your starter Pokemon.

2. The man in the house on Route 30 gives you an Oran Berry.

3. The Treecko from the lady in the secret National Park area is holding an Oran Berry.

If you're playing a beta in which the fruit-bearing trees do appear, then just check them to see if they are holding Oran Berries. Trading Oran Berries over doesn't hurt either.