I would not be able to afford special B12 if I could find it. Do fine 3X a week with my source of non-prescription cyanocobalamin.
Of course, this may be because I use the Moreless ideas from that CZ forum to enable my body to have enough major and trace alkaline minerals in the right forms to function better!
B4 doing ML, I was going into the kind of details you mention here and working myself into an unhealthy state of worry and stress.
Are you sure you need this? Why? Who said so? Have you checked any other opinions?