first off welcome to the site
and to be honest I have never really ever seen anyone mount them to the front of there atv's
as it would just lower approach angles so much so most don't want this! so most likely one of a few reasons your not finding any
also, would be a LOT of leverage would be on front end and make steering harder and really lower the front end of your atv , with just a few hundred lbs of tongue weight!
simple light weight snow plows make a front end sag pretty good, and many times require HD springs to help and you still get some sag!
A hitch to be able to push boat trailers would IMO have to stick out farther and that again would lead to more leverage on the front end making that sag even more so!
BUT I am sure if a guy wanted to ad one, they can be made!
IF I wanted to make one, I think I would start with a ATV Snow plow MID mount plate
add some 2 inch tube and then some how tie off the front frame down to it, this way more of the weight will be on the center of the atv and NOT just the front end!
I couldn;t tell you if the work to make one would be worth it, over just backing up a trailer the normal way?
but this is as always a personal thing