Tablets’ Display Size; are we limited to small ??

Hiya 2 all,
I have been tasked with finding a tablet pc for an older gentleman who really wants a larger screen than these 12.5″ that I am finding w/G searches-ha, wish me luck !!
Does anyone have a clue as to a Tablet PC mfg. that will offer the larger sizes, like a 15″-17″ ??
Thanks, I appreciate any input-T Mike