You know there is a good account of how COL Bell escaped prison after capture at Helena. Quite detailed but I can't remember if it was out of the Confederate Veteran or another source. I may have a copy of it somewhere. Are you aware of that?
And of course, a flag of the 37th captured at Helena is now viewable on the Iowa Flags website.
COL Bell's grandson is still alive I believe. I used to talk with him quite a bit. I believe one of his sons still has some of the Col's personal effects from the war.