Here, I am giving you cheats for use in VBA.

But you said that codes at gamefaqs might not have worked
because you might not have the latest version of VBA.
Download latest at vbalink.info

Go to Cheats>>Cheats List>>Gameshark.
Here, write the following as the code.

E1F2DD6004576E50

The above code is anti DMA.It needs to be activated for the codes to work.
To activate anti-DMA you will have to enter any building.
I suggest to enter Pokemon Center as you can access PC there.

Then go to Cheats>>Cheat List>>Code.
Here, write the following as the code for 99 Master Balls as the 20th slot of PC.But beware that you withdraw the 20th item otherwise it will be gone forever.

02025EE4:00630001

Withdraw as many as you want then, disable the code.

Then go to Cheats>>Cheat List>>Code.
Here, write the following as the code for 99 Rare Candies as the 20th slot of PC.

02025EE4:00630044

Withdraw as many as you want then, disable the code.