Welcome to the Forum Griz -
Stocks for the Howa 1500 / Weatherby Vanguard are being produced in mass now in the after market. Several makers are producing good, drop in styles like Bell & Carlson here in the US and Prairie Dog Rifles Stocks out of Australia.
There are also several custom stock makers out there that will craft you a custom built rifle stock, but they are pricey and the wait time is a bit of a pain in the rear.
I would be concerned with your 16" estimate though. I have a long reach and my stocks are 14.5" to fit for summer clothing and I take .5" off for anything winter related in my part of the country.
Have you actually measured your correct length of pull? Because the average, here in the US, is 13.5"