You might want to start at Central Market where there are several dealers stocking a mix of genuine antiques, such as keris, sundang, spears, swords as well more recently made keris from Java and Madura. Look for a shop called Kelantan Silver which has a selection of weapons. There's another similar shop upstairs run by the same owner.
Since it's a touristy area, prices can range from fairly OK astronomically unreasonable, so caveat emptor.
Then, there's always Ahmad Toko Antik, a small antiques and curios shop somewhere in Kampung Baru. It's a bit hard to spot so you might want a local to show you the way, it's within the Sunday Market near a block of flats. The old man has a good selection at fairly reasonable prices and you can always stick out your neck and haggle. The owner, Haji Mat, is known among the collecting fraternity here as an old man with an unpredictable temper. On good days, he'll let you have a good keris for a song, on bad ones, he just padlocks the shop saying he's off somewhere. Quite a character.
I'd go there just to savour the experience.
Of course, there's the network of dealers and collectors who don't ply their trade in proper shops, but for that you have to know someone who knows someone, who knows someones cousin's brother's sister in law
