The gypsies in Lavastorm sell these for about 30p each. You can get them free in Erud's Crossing, or possibly from killing that brownie in Rivervale, but the extra cost is worth it if you don't feel like doing a lot of travelling.
Before I had a pair of these, my fire resistance was 38 (Iksar have higher base fire resistance) and falling in lava would cause 38 damage a second. With these, it's 48, and I take 34 damage a second. Not a big difference, but it's getting there. If you plan on going to places like Solusek's Eye or Nagafen's Lair, it pays to have a lot of items that boost your fire resistance. This is a cheap and easy way to get an extra 10 sv fire. (Enchanters, I suggest using dry bones illusion in these places, gives you an extra 25 fire resistance!)