VPI no longer supports the HW 19 tables but you could contact them about buying any plinth they have left over. The plinth from those tables is a laminate of several materials if I remember correctly.
You sound like you are handy and, if that's the case, you can use the parts from the VPI to make your own table out of any material you feel like messing with including Corian or granite. On the other hand you could just extend the hole in your current plinth so the it extends back about a half inch. There is about 7/16 of an inch difference in effective length that you lack. If you were to drill the arm hole so that it was a long oval, you would have enough length and the base collar of the arm might even conceal the extra opening. I have seen designs that leave room to slide the arm mount for adjustment. Should be fine.
You sound like you are handy and, if that's the case, you can use the parts from the VPI to make your own table out of any material you feel like messing with including Corian or granite. On the other hand you could just extend the hole in your current plinth so the it extends back about a half inch. There is about 7/16 of an inch difference in effective length that you lack. If you were to drill the arm hole so that it was a long oval, you would have enough length and the base collar of the arm might even conceal the extra opening. I have seen designs that leave room to slide the arm mount for adjustment. Should be fine.