I will say that for some odd reason, Jayde is one of the most difficult potencies to find. It does not seem to drop in the zones it should drop in, and it is rare in the Guild Stores. While I have more than a 100 of most every potency in the game, and more than 50 on the ones I don't have 100, I have like 6 Jaydes and have never had more than that many ever.
I think the advice above to buy the finished glyphs of that level and deconning is the way to go. The question is, and I have never tried this, is if you buy Glyphs from the Enchanter NPC Merchant, do you get any Runes back on decon? You may have to hunt for them at guild stores, and they will be rare as the potencies are rare.
At least when DB drops and you can buy Potencies, it will alleviate this issue for these pesky L3 Potency Enchanting Writs. I personally specced my character up to L4 as quickly as possible because of this.