Haircut for husband by a Nida woman

Thank you.

I'm talking about a haircut in a place where the man needs it because of his personal feeling, not just because of the mitzvah.

There's another point here, that a haircut with a hair clipper does not require actual contact, because the woman touches the machine, and the machine touches the man.

As I wrote, I don't think it's really possible to ban it. But I don't think it's appropriate to do so just because of a holiday haircut. If it's an extreme inconvenience, maybe so.

And after the holiday, will it be permissible to get a haircut during the days of reckoning?

If it is very disturbing, then there is room for leniency (the prohibition of a haircut is one of the first and not from the Talmud). In general, it is forbidden to cut a regular haircut that has an aspect of joy, but it is permissible to cut the mustache if it interferes with eating. Likewise, someone whose long hair causes him headaches or has wounds on his head, and I suppose even if it is very disturbing without wounds, is permitted to cut his hair on these days (Shulchan Tikva, 13; Tikva, 8, 42 21, and in the above Ibid).
Remember that this year, the eighth of Iyar falls on Shabbat, and according to Ashkenazi custom, it is permissible to cut his hair on the eve of Shabbat. See 42 57 58. That is why I would wait there, and that is the most convenient.