just saw your post, I have got gamelan instruments direct from the villages where they make them - One village called Sawan is in North Bali - you travel east of Singaraja and just past Sangsit you have a turn off to the south and about 10 km along is Sawan. I have bought a cheng-cheng there.
The other village is called Tihingan and it's in East Bali, with the turn off between Gianyar and Klungkung. I have bought a gangsa and priest's brass bell there. They are happy to show you around their foundry's and it is very interesting. There is a gamelan instrument maker in Denpasar, but it was back in 2004 and I don't have the address. I bought a large gong from there. Make sure anything you buy which has wood is free of holes. Good luck with your shopping.