By lore a member of the Order should have some Sorcery Power.
Lastly, each prospective Dark Moon acolyte had to demonstrate some sort of sorcerous power.
Way of the Four Elements lets you use ki to infuse elemental aspects to your attacks. Gwmort's suggesting that that ability could be justified as the "sorcerous power". I don't think you need the wisdom for unarmored defense, though, since you can go draconic bloodline sorcerer to get a 13 AC, which you'd need a 18 wisdom to exceed. Draconic Sorcerer will also get you 1 hp per sorc level, so that helps a tiny bit with the con issue. There are problems that remain, though. One thing is saving throw DC for the enemies, as well as to hit bonus for the sorc half. These want wis for the monk stuff, and cha for the sorc one. You'd probably have to pick one or the other to focus on. Gear would also be a bit torn. Another issue is that elemental monks aren't half-spell casters, so that would limit spell access, while the sorc levels mean fewer ki points, which really hurts the elemental monk. And, of course, cha impacts your quantity of ready sorc spells.
But let's see, as to how I'd go about it... I'd start with a level of Sorc, Draconic Bloodline. Stats would be 10 str, 17 dex, 14 con, 8 int, 14 wis, 12 cha (though maybe flip wis and cha around, depending on how you feel it plays). Then probably a level of monk for flavor, followed by 3 more levels of sorc to reach your first feat, which would be War Caster. The reason why is Enlarge, which should let your monk do an extra 1d4 on all his unarmed strikes. This is a concentration spell, so you'll need con saves, and War Caster will help with that. The Shocking Grasp on enemies moving out of range will also aid with the "I'm a sorcererous monk" feel. Sorcs also get con as one of their proficient saves, so that will help with that as well. For meta-magic, you'll probably want Twin Cast, so you can Enlarge another melee, and Quickened Spell, so you won't burn your main action to cast Enlarge.
From then on, I'd go monk for a while, with the Open Hand. Why Open Hand? Because the abilities only cost 1 ki, so you can get more uses of them, and punch 2x, so more benefit from Enlarge. And you'll get that benefit even if the enemy has an easier time making their saves due to your lower wisdom. Now stick with Monk to at least monk 5 to get the extra attack, as well as another feat at monk 4. That should be Ability Improvement if you got the hag hair to boost dex, so you now have 20, or else Resilient for dex if you didn't, for better saves and 18 dex. Either way, you are boosting both AC (so you get hit less often, so fewer concentration checks) and hit more. Probably should go all the way to Monk 6, for the magical unarmed attacks and Manifestation. And now you have a choice. One more level of sorc gets you haste, so you could use that instead of Enlarge, but this would mean no feat at 12, which could be Tavern Brawler, if you want to use some item that boosts your strength, like if you've been stockpiling potions. Haste also has more severe consequences if it gets broken. But you could twin-cast it, so there's that. Or just stick with Enlarge, and keep trucking along. And all monk levels for the rest.
Gear-wise, you'll want The Graceful Cloth sold by Lady Esther, for the +2 dex ,so don't pick a fight with her, and, of course, various things that add to your damage.
