Why don't you build yourself a armboard out of high grade marine grade plywood? The Simon Yorke turntable uses this material for their armboards.
Arm board recommendations for SOTA
I am getting back into analog and have purchased a SOTA Star Sapphire and an OL-modified Rega Rb250 arm. I will need an arm board and SOTA offers 3: laminated MDF at $70, aluminum/acyrlic composite at $149 and Cosmos (aluminum, acrylic and lead) at $250. Any thoughts on bang for the buck here, or any other options? Thanks