The purple lvl 45-50 fire resist glyphs give 1000 fire resist. The vr1-3 purple fire resist glyphs give 1000 fire resist also. I've yet to see any rings or necks with fire resist on them before an enchant is applied. Granted i'm still only at Coldharbour and there may be some that drop in veteran zones. The closest i've seen is lightning resist (thunderous knight set or something) and spell resist which was on another set piece ring/neck.
Get yourself one of the fire resist glyphs as mentioned above. Then buy an enchantable ring or amulet from the vendor in the Mages Guild (they don't cost a hell of a lot) and enchant it with the glyph. Job done!