Second Andy's remark about the BMX term. That makes me picture a one piece crank! I suspect something like Origin-8 Singlespeed/Fixed Gear Crank Set w/ 46T Ring. Black - Harris Cyclery bicycle shop - West Newton, Massachusetts
would be apropos. That is the crank I used on the 3 piece conversion of my old Columbia Sports 3, and it has served well for several thousand miles. Bottom bracket is an inexpensive UN55, IIRC. I think it was very narrow, maybe 113 mm, to get a good chain line. I realize you specced a 44 tooth chain ring, the crank I linked to is 46 tooth, I did wind up putting on a smaller ring. Don't remember if it was 44, though.
Anyway, the crankset will determine the width of the bottom bracket needed.