This is why I suggested that you try to "buy" the head unit you want there too. If you find the HU you want, add it to your cart - after you tell their system what your truck model is. Go to "checkout" and look at the additional harnesses that they've included on your invoice for free. Obviously, don't consumate the sale, just get to the checkout so you can see what harnesses they were going to send you if you did buy it from them. Each of these harnesses should have a hyperlink to them so you can look at photos of them and maybe even see some specs on them.
The wiring harnesses that they give you for free, are theirs, Crutchfield house-brand. I've never been able to pull up a stand-alone wiring harness there either, but they always have a house-brand type available. From that, you may better be able to figure out which type/kind it is that you'll need - since you said you found several, with a wide price range, out on the internet at large.
EDIT: I just went through their harnesses, and when I plug in my truck (08 T4R LE with Factory Nav) they show no in-dash receivers that are compatible and none of their Toyota harnesses (I found 2 out of the 103 they carry) said they were compatible. Sounds like you're going to need to call Crutchfield or some other radio supplier and talk to a live person - maybe they can deterime compatibility for you and recommend a specific harness or harnesses.