This is a great edition to this post. Now that I've got time, here's what my original response was before Tumblr ate the damn thing.
With eBay - the "Worldwide" function is best if you don't want to interact with sellers, because they're already willing to ship internationally. ebay.de is your second best bet, like BTP mentioned above.
On the subject of eBay, here are some seller pages of note. Every once in a blue moon they might have EA-related items.
Emilie's former Trisol manager, "Bunny," also has an eBay page, but I believe he sold off his backlog a few years ago. It also appears EA shut down her personal seller page on eBay. But buying CDs from Emilie herself is your absolute best bet for anything to be guaranteed legitimate, so watch The Asylum Emporium from time to time - but keep in mind that while they do come from and directly benefit her, she does inflate the prices. (At least they tend to be autographed, though.)
I've had the best luck finding random things - namely German DJ singles, album promos - on Discogs Marketplace. They are by far the most specific with their listings. Lots of personal collections from DJs and brick and mortar stores.
Projekt still has the limited edition, digipak release of Girls Just Wanna Have Fun & Bohemian Rhapsody EP on sale for under $5. I reached out to them once and they had a substantial stock.
I've also had random luck on Amazon. The same with eBay, you can visit the international websites and reach out to sellers to see if they can ship to you. Scour the "used & new" pages. In my experience, I've found Traitor Records Enchant and the Opheliac EP on Amazon for decent prices. But I did have to reach out to sellers directly to get photos and info.
As far as what's most likely to find on what website? It's a crapshoot, especially for Enchant and pre-Enchant era stuff. Most of what you can find will be European-based sellers that have Trisol Records in stock. American sellers tends to have the early stuff.
Bonus info: check library listings. If you just want to check things out or see them, I have found random and rare items on library listings online. Especially in the Chicago and California areas. You won't have much luck purchasing anything, but you can take a look.
Edit: Also worth noting, IronD copies aren't technically illegal. Trisol sold off the rights (or whatever the term should be) to the albums years after their split with EA. Emilie was unaware and publicly denounced the distribution, which is why they're widely considered bootleg. (However, the Chambermaid bootleg is a true bootleg to my knowledge.)