In the record of the July 17 and 18, 1962 "Qualifications for Astronauts" hearings before the special subcommittee on the selection of astronauts that was organized to know if women could become astronauts, Mrs. Hart shows some pictures to the members of the subcommittee. What pictures did she show? Are those pictures archived somewhere?
If you skip forward to p11, there's a transcript of her description of the images - it looks like there were three pictures, all connected with the isolation tank tests. It's also worth noting that it was Cobb showing the pictures, not Hart.
(Pictures.) So with that we will go ahead with the slides and I will briefly describe these as we go through them.
(Slide.) This is the recording chamber for the isolation test, where they keep continual tape recordings going, listening to every sound, even the breathing sound, so they can tell whether you are awake or asleep. The doctors in attendance record everything during the run while you are in this enclosed room submerged in the water.
(Slide.) This is when I got out of the tank during the debriefing temperature and blood pressure and everything. Go on to the next one.
(Slide.) This shows what the tank is like. The water is perfectly controlled to temperature of the human body so that you don’t even feel the water. Actually you feel nothing and float in this tank in total darkness where you cannot hear, see, touch, or smell anything.
Specifically identifying these pictures is probably impossible unless the slides were archived with the committee papers (which is possible, but likely to be in a box in DC somewhere if so...). Via this Wellcome article, though, I think I have found some candidates, published in Life, 24 October 1960: it has three photos identified as Cobb in the tank (any of which could be her third picture), and one of her having blood pressure tested afterwards (which sounds like her second). It doesn't have anything matching to the first one.
This article (taking stills from a PBS documentary a few years back) has a better quality image of one of the tank photos, though they identify the woman in it as Funk not Cobb. I think this is probably an error and the Life attribution is correct. (There is another photo in that article of someone wearing scuba gear in the isolation tank; they have also labelled it as Funk.)
There are one or two photos knocking around of Cobb at other points during testing (eg Fig 4 in this article) but these are the only tank ones I could find.