Aluminum or Wood armboard for Technics SP10 Mk2

You might even have one made for you out of slate, for very little money. You would have to drill it yourself, which is messy but do-able. (Lots of dust.) Otherwise, I kind of favor hard woods or a laminate of wood and metal over solid metal. But my opinion is based on no data.

NOS (undrilled) Technics boards appear from time to time. Depending on your perspective, at over $300 they may be considered expensive. There may still be one on Audio Asylum Classified.

If I was in your situation, I would be tempted to have 2-3 different boards made up (easy enough to trace your original board for dimensions and mounting holes) then see what sounded best with the new arm/cartridge combination. I'd likely choose solid wood (maple, spruce, etc.), aluminum, and acrylic since they are so different.