In particular, I want to know where other manippers get the original pics for their manips but I welcome others to post the sites that they frequent for content.

I get my source material from either Danbooru, Gelbooru, Sankaku Channel, Pixiv and occasionally Exhentai. I recommend any of those sites for others.

Hrm... for original pics, I'll peruse /d/. For R34 pics, my go-to place is the Rule 34 booru.

I use gelbooru, mostly.

Gelbooru and Pixiv.

I actually, when I am in the mood to make a manip look on 4chan. If you have the stomach to endure the worst of the worst, you can often find some amazing stuff burried under all the crap.

Gelbooru and sometimes sankaku, though they mostly have the same images, and SC is kind of a bitch to navigate with so few images per page. On the plus side, they both have very extensive tags, so if I get an inspiration for a specific type of manip, it's pretty easy to find images that match that idea (headphones, yuri, etc.).

There's also hentai-foundry, but that site is so iffy in the tagging that it's pretty much torture to find a workable image. It's a shame, considering it's probably the internet capital for drawn smut for western artists.

Not much of a fan of Hentai Foundry. I've seen several artists with incredible art quality (and sometimes better quality than the site's enter art) complain they cant get their art through their quality control barrier.

I might just be finicky but it gives the site an uncomfortably stuck up feel.

Pixiv and Danbooru/Gelbooru, who also get their pics from Pixiv. So, just Pixiv.

Since I made this thread I figure this would be the best place to ask this question. Does anyone know if there is a Japanese version of this site anywhere? I don't mean one exactly like this but just a sort of equivalent where hypnofetishists converse a share content exclusively with each other. I know for a fact that Pixiv's search engine is just as bad as DA's so it's not the best place to find specified content.

*shakes head* As far as I'm aware, there is not one. I've looked before, too.
The closest thing I found was the occasional (every few days) Hypno/MC thread on this Japanese chan board: jun.2chan.net/b/futaba.htm It has a pretty solid following of people that seem to constantly inhabit its every incarnation.

There are manip threads there, too. If you look thoroughly enough, you'll sometimes find some pretty useful props. I've been skulking around there for a while, harvesting any props that are posted.

Anywho, I get most of my manip material from Pixiv. I tend to check Pixiv 99% of the time compared to other sites. I hardly go anywhere else, nowadays, except maybe weekly or monthly (depending on site) just to check on new potential hypno snuff.