H Authur...

First of all...anybody claiming to sell you a waterproof backpack in Malaysia is either a cheat or someone who is trying to rip you off.
There are no 100% waterproof backpacks. Certainly not in Malaysia. For fully waterproof carriers, you should look for dry bags.
There is a brand that I was told recently makes really good waterproof packs. The brand is Arc'teryx but they are sooooo expensive. You can only get them at Camper's Corner in Singapore. Be prepared to pay anything around RM800 to RM1500 for a pack!

My suggestion would be for you to try on a few models. Think about what things you are going to carry and see if the pack you like is big enough. If its ngam-ngam, get a bigger one.
Once you have your backpack, you go get a dry bag. The dry bag is for your water sensitive gear like digital cameras, ipods etc.

Most packs these days comes with hydration sleeve for your water bladders. No problem.

KEONG

Hi Keong

Thanks for the suggestion.

Any idea where I can get the bag which you had just described?

Cheers