The tableside mount on my original is a little offset from center. I still have my original table but it has warped a bit from moisture (live in Florida). I bought a replacement plastic one from Amazon and made a thin solid wood template to set the mount 6.25 inches off center. Works perfectly and actually looks better than the original and I love it has can/cup holders in the replacement.
This is the one I got but really any 18 X 30 oval would work to match the originals size.
Springfield Marine 1670006 Table Top - Oval, 18" x 30"
Amazon.com: Springfield Marine 1670006 Table Top - Oval, 18" x 30": Automotive