Tenergy sells LSD true D, C and 9v cells, as well as AA and AAA. Their LSD D cell is rated at 10 Ah.
By "true D" cells, I don't think you mean I could place four of the Tenergy Lithium Thionyl Chloride D 3.6V's in my unmodified/standard 4D CCRadio2 or MagLite and would be good to go. To be clear, if you couldn't or shouldn’t, then they’re not equivalent or true.