I bought a TNF Nuptse down jacket at a jaw-dropping price, and the reason is it has a 1/2" tear at the bottom of the jacket at the seam.

Currently it has non-sticky tape to hold the down from escaping, but it's definitely not a solution. I've researched a bit and all I get is using the nylon repair tape - in all other colours but what I need, brown. And they say it's not a permanent solution, just a temporary.

Do you have any suggestions on how best to remedy this? I can stitch it, but if it ever gets wet, it's not such a great idea, is it??