The part number is contained in the movement parts list which I found in a number of places on-line. Thank you for the offer of help. The part number is 0963300 which is common to both of the movements. My reason for seeking out a part is not because I currently need one but because I wish to properly prepare for modding my SKX007 with a new movement. Yes, I've decided to keep it and upgrade it. Let me heirs (hopefully far in the future) worry about disposing of my watches.
Hopefully, I won't lose or damage the clip when I remove and reinstall it as I exchange the day wheels. That said, I have a long and rich history of doing just that. I remove such items inside a plastic baggie if possible just to keep them under some sort of control. I'm not always successful so in addition to acquiring a NH36 movement, I'm also going to have a good idea where to find the e-clip should I need one.
Breaking out my calipers may indeed be the correct route as I have no idea what the correct size is, except it's very small. I can't help but wonder if SII would make such a part in house or purchase it as a standard, off the shelf hardware item. If so, it should be available somewhere other than through Seiko.