OEM hitch, yes. Harness from etrailers, much less expensive. You can buy the hitch from Acura of Peoria (AZ). I picked it up there, but they ship. I have read that their internet price is the best anywhere.
I had a 2015 MDX and put an aftermarket hitch on it and never liked the way it hung down.
My OEM hitch came with the receiver twisted, a bad welding fixture I suppose. There has been at least one other report on this forum of same, so be prepared the possibility for that. The effect was that when I mounted my box it went slightly downhill to the right, when viewed from the back of the vehicle. Some people might not notice this but I have a plumb bob built into my brain and I didn't like it. I shimmed the mounting frame of the box, a simple thing to do, and it is now level and my brain is happy.
You can look on-line with other dealerships, Acura auto parts online, or eBay for the best price. I would take the best price (with shipping included in final price) to the parts manager at your local dealership to see if they can meet or beat that prices. You have to pay sales tax; but, the dealership can most of the time get you free overnight/2nd day shipping and give you a break on install labor if you have a long term relationship with them.
I've purchased several items from Acura of Peoria (Az) via their internet presence where they shipped them to my location. I've been happy with them and their discount. I purchased a roof rack from a different Acura dealer via Amazon and that was a good experience as well.
I was disappointed at the high charge the local dealer wanted for some items - they were marked up higher than retail from what I recall. I told them they could just have the parts back since I wasn't going to pay that extra high price. They ended up honoring the lower price, matching the internet price, but possibly only because they didn't want to go through the hassle of restocking the items (I didn't notice the high price until I got home).
It's easier to just buy via the internet and have it shipped based on my experience with my local dealer. Maybe another dealer would be better in this regard.
I agree with mdxstang about buying over the internet being easier. I have been doing it for a long time and don’t recall ever having a problem. Getting a fair price from a dealer as a walk-in is sometimes an adventure, whereas over the internet pricing seems to be more up-front. I found this to be especially true with BMW parts departments, which often set prices above MSRP.
I happen to live in Phoenix in the winter, not too far from Acura of Peoria, so I have dealt with their parts department on a walk-in basis, and I ask for the internet price and they give it to me. I hate to write the following, because as soon as I do it will probably all go bad, but Acura of Peoria seems like about as good a dealership as I have done business with over the years, either for parts or repair - no funny business, so far.