GTN style insert up to 32mm diameter - https://www.shop-apt.co.uk/part-off-...2mm-shank.html

WDN style insert up to 26mm diameter - https://www.shop-apt.co.uk/external-...max-depth.html
(APT do do a 32mm version, but they're showing as out of stock)

I personally use the WDN style, as I couldn't find a reasonably priced 12x12 shank holder for GTN types when I was originally buying holders.