I have several 4x naginatas in stock, and am making some more. I did have a 5x but sold it; my current major enchant project is a maul, so it would be a while before I'd have another one. But yes, all the naginatas are further enchantable; flares are up to you and either a merchant or using premium points. Price for a 4x is 250,000, which is 1/4 the cost if you bought it from the weaponsmith in zul Logoth. I also am in the Landing.

The bells of Hell
go ting-a-ling-a-ling
for you but not for me

as far as flares for a merchant to flare one its over a million fee, last 4x flared nagis were 1.5+ off the shelf. so premium points are prolly easiest way