| Ryze Kuja |
Tetori Monk is the best grappler archetype. If you want your DM to cast the legendary spell DM Flips Table, multiclass into Druid for the "Monk-topus" build.
Tetori archetype isn't compatible with Umonk though, you'd have to go Chained Monk.
If you're deadset on being a Umonk, you can always just pick up the Grapple Feats and you'll still be a highly proficient grappler regardless. You can pick up the Elemental Fist Ki Power and the Electric Eel Style feat chain.
| Doompatrol |
Honestly the best advice would be to treat grappling like an option, not something you dedicate your build too.
Better to be good at damage and grappling rather then really good at grappling but mediocre at damage.
Pick up the basic grappling feats and maybe the first electric eel style feat for when you want to grapple, Dragon style for when you just want to punch people.
| Derklord |
Wait I may have found something but I am not sure 100% if its first party or not.
http://hastur.net/wiki/Unchained_Monk_Archetypes_(Apath)#Tetori
The site says "Unofficial rules compendium" in the top right corner for a reason. Zero pre-unchained archetypes are first-party-legal for unMonk, and only a part of those released afterwards. Here is the full, exclusive list of first party archetypes aviable for unMonk.
The archetype from that site seem to be a significant upgrade*, as it doesn't replace Flurry of Blows. It looks like it would make for a character who's good at grappling yet still able to be excellent at regular combat, which is certainly desirable. So certainly worth asking your GM.
*) Over the cMonk version, not necessarily over vanilla unMonk - depends on the campaign which is stronger.