I suggest you look at the Cloak of Comfort which gives you and all allies within 30' of you Endure Elements as well as resistance bonus's to saves. It may be found in Complete Mage.
Well... if you have a DMG, you should be able to calculate this yourself pretty easily.....
But sure, why not... I'm bored.
1st level spell at caster level 1, continuous item...
Looks like 1x1x2000gp. Then you check that its 24 hr. duration, so divide that in 1/2..
Looks like it should cost about 1000gp And for an effect like Endure Elements... Sure, why not? I doubt it'll break anything
1000 gold sounds about right to me also. Maybe should be mroe if you are going to be in extreme temperaturs a lot. I would be loath to allow it in a desert-themed game, for example.