Here is my bookmarked link for the GoBusters search
, they have Ace for 3500 yen.
The biggest difficulties with Mandarake is so much of the stuff is only in Japanese, to get good search results you almost always need to search with Japanese text, for which I've used Wikipedia to get series names, and then if the image isn't clear enough, I copy/paste the product info into google translate to make sure I'm getting what I want.
The other problem is no up front shipping estimation. You have to choose credit card payment if you want SAL, but I don't have a problem with that.
Also, be aware that items are actually in different store locations, and orders across multiple locations cannot be combined, and they charge a 500 yen handling fee if the order subtotal is under 5000 yen. It's not usually been a big deal to me. The first several orders I placed I made sure were over 5000, but lately I've been fine with the 500 yen fee, if the items are cheap enough its better to pay the fee than spend a lot more.
But it's seriously my favorite online store right now. I'm somewhat sheepish to admit I've probably placed 10 orders there in the last 6 months, if not more. Actually, probably more, I think I have three in transit right now, Ace, SIC Den-O Sword Form/Momotaros, and I think I placed an order a couple days ago with SH Wing Form Den-O and the last two OOO Combo Change figures I needed.