Marma,
I have one from Outdoor Products. It doesn't have any metal parts, but you might want to send some extra bite valves.

You can check their site and find a retailer in your area: www.outdoorproducts.com . The company has been around for a long time.

Mine is 1.5L pack and for me that is adequate, light, good for biking and hiking but doesn't hold much extra gear, so you might play it safe and go for a 2L.

Also, some of guys I hike with recently bought similar looking packs at Wal-Mart for only about $18 and they seem fine.