Mega Evolution Pokemon in Pokemon Sun?

Question

So, I'm finally playing Pokemon Sun entirely after everything has been spoiled, but, I managed to keep myself unspoiled. So, although I'm not 100% sure if Mega Evolution is in the game, but, I would like to have a Pokemon capable of Mega Evolution in my in-game Party. To give a bit of context, here is my in-game team so far. You can simply change a slot for the Pokemon you feel that can fit. If you can, please suggest the Pokemon and where it can be found on the one of the islands. I know now Mega Evolution is post-game content, and that's fine, I'm simply wondering are there any Pokemon I can catch now before then, and where can I find them. Like, for example, Haunter, Electrike, or Sableye. (I'm right smack-dab in the middle of raiding the Aether Foundation's headquarters as well.)

In-game Party:
Incineroar
Mudsdale
Alolan Persian
Happini
Aquanid
Electabuzz

Thanks in advance if you can help me.

Comments

Mega Evolourion is post game, sorry.
Source: experience

---

This doesn't answer the question. He/she/it asked for a Pokemon that can mega evolve even if he/she/it can't mega evolve it until post-game.

---

Thanks for editing this, even though it took much more time than it should have, HT!

---

You still didn't fix anything I told you about >:(

Answer 1

Here is a list of all Pokemon who are or whose evolutions are capable of Mega Evolving that you can catch in Alola, in Sun and Moon, before the post-game.

Slowpoke at Routes 1, 15, 16, and at Kala'e bay.
Abra at Route 2 and Hau'oli City.
Gastly at Hau'oli Cemetary, Memorial Hill, and in Poke-Pelago.
Magikarp at Routes 7, 8, 9, 13, 14, 15, Melemele Sea, Kala'e Bay, Seaward Cave, Paniola Town, Brooklet Hill, Secluded Shore, Tapu Village, Malie Garden, Poni Wilds, Poni Breaker Coast, Seafolk Village, and Vast Poni Canyon.
Sableye at Ten Karat Hill and Vast Poni Canyon.
Bagon at Route 3 and Kala'e Bay.
Kangaskhan at Wela Volcano Park.
Pinsir at Lush Jungle and in Poke-Pelago.
Beldum at Mount Hokulani.
Gabite at Haina Desert.
Absol at Route 14, Tapu Village, and Mount Lanakila.
Snorunt at Route 14, Tapu Village, and Mount Lanakila.
Sharpedo at Poni Breaker Coast.

Hopefully this helped.
Please let me know if I missed anything that is available before becoming Champion, or if my information is incorrect.