Kenwood 500 turntable arm set up.

@reched viridian is suggesting a very good idea, but I would expend on the Materials being used to produce the TA's Base Board.

Start with what is quite cost effective of which one option is already made known.

A Newplast Modellers Putty can also be added to the Underside of the Base Board material to substantially improve on the Damping Properties.

The Better the Damping for the mounting of the TA, the better the Cartridge will be catered for, as the local energies that are present, will have their Amplitude reduced or improved as a management.

The synergy that really impresses between the combination of materials will be discovered for one being quite unimaged for the valuable impression made.     

There is seemingly plenty of options to have a talk with a Service that is local and will make easy work of producing a Part, it sounds like a Apprentice Pin Money Job.

Companies like their Apprentices to get a chance to express themselves and have a little responsibility.

Private Jobs like this one, do not mean costly, usually quite affordable. 

https://www.google.com/maps/search/engineering+machine+shop+in+north+carolina/@35.6202985,-81.5402989,8.75z?entry=ttu&g_ep=EgoyMDI1MDYzMC4wIKXMDSoASAFQAw%3D%3D

If going the Wood Working Route, the selection of 'Resin Impregnated Densified Wood Board' Material will be a great choice.

I'm sure there is  Gon Member with a small Off Cut that they can part with.