Ramon,
I know you weren't asking explicitly about my wire specs or source, that information would not directly help a competitor anyway since those specs are specific to my processes.
Welcome to the world of fine wire handling, what you have is at the bottom range of the mid-size diameters, Evanohm can be drawn down to a mere ,0004" diameter and if you think .0012" is tough to see and handle, try some of that <grinning>. Some of the Evanohm variants are quite stiff and do not like to be wound around a small form, they will spring like a clock's main spring if let loose and it is a mess to straighten out. Handling is difficult to say the least with the finer wire sizes.
The standard specification of TCR for Evanohm 'S' is 0±5PPM/°C, meaning that a given spool of wire can be anywhere within ±5 PPM and considered in spec. Indeed a given batch of wire can be any TCR within that range, if it happens to be 0 TCR, they just happened to hit the mark during heat treating, it is not a real precise process and depends a great deal on the knowledge of the heat treat process and the alloy. You can certainly 'order' a spool of 0 TCR but it isn't going to be cheap, base pricing is calculated upon the standard ±5 PPM spec, when you ask for a specific TCR, the marketing cash register starts dinging big time, the price is near exponential as the TCR approaches zero TCR.
Carpenter is quite possibly the most difficult alloy source to deal with, they absolutely do not like small potato buyers, I've had quotes from them and you will likely end up with something on the order of 10 lbs minimum unless they've changed lately, that is a lot of wire. They will provide your spec willingly if you buy enough wire. I generally do not see very much Carpenter alloy on the 'surplus' markets, why I don't know for sure, they are one of the largest alloy suppliers around along with Kanthal. You were very lucky to find a spool with a zero TCR on it, those are relatively rare as the original owners usually won't part with that TCR wire. Be advised, like most alloys, cold working the alloy will change the apparent TCR, it is a mechanical stress and adds to all of the other mechanical stresses that accumulate during resistor manufacturing. As I've noted before, the finished wire TCR is inherent to the wire and cannot be changed by normal resistor manufacturing, it is the mechanical stresses introduced during manufacture that make the overall apparent TCR different and depending on the resistor manufacturer, they will have come up with various ways of trying to reduce that stress with varying success.
The wire enamel (and there are several classes of enamel) won't have too much effect on the 'ease' of handling it.
The short answer to your wire buy request is no, as I noted above, Carpenter's minimum is large and 0±1 PPM TCR would definitely be a special order from any wire source, including mine. What TCR you end up with on a 'finished' resistor will be different than the ±1 PPM/°C you started with. I am not trying to dissuade you from trying, I'm just trying to let everyone know how difficult it is to achieve very low TCR, there are so many variables involved, you just might get a resistor here and there with low TCR but it will likely be by accident. The wire is only the beginning.
If I could persuade my supplier to produce 0±1 PPM wire, their minimum purchase will run pretty close to $600 my cost and depending on the wire size, how many feet that will get us won't be known until the quote is made. If you can persuade enough people to purchase enough of the spool, I can absorb some of the wire myself if it is a size I need.