There is a pretty good pic of the saber in the Ep1 Visual Dictionary on Mace Wind's's page.
Above the extra rings, there is a short neck and a short 1.5" thick (same as grip rings) section that are the same "color" as the main body. Then comes the shiny emitter.
I think a lot depends on the type of Maul saber you get. Also, do you want a polished saber or one that is half-grey/half shiny? I guess you could make the extra grip rings part of the piece the machinist makes for you.
Also, the covertec clip on Plo Koon's saber is on the thick section closest to the lengthwise ribs, not on the next.
But then I guess you will use the half that does not have any covertec clip attached.
You will also have to fabricate the knob that the holy disc sits on.
I am not an expert on this saber, nor on machining. I have built the Adi Gallia/Aayla Secura saber from hardware with rings that were slid on, so thought I should share that tip.
I have used anodized aluminum vacuum cleaner tubes. They are thin-walled. The section where these pipes connect can often be 1 1/2" thick - which would be the same as the ribbed section. If your source saber is anodized, perhaps the scheme I proposed could work without having to paint the saber silver/grey. However, there would be exposed metal at the edges but I think you could cover them up with a black wash for weathering.