If you know the Toyota part number for the connector housing, you can use just the last five digits - you can find it by using the search tool on their site. If they have it, it'll pop up. However, there are kits they have assembled which have not only the connector housings, but also the terminals and seals, which the search will not find, because they are not listed by the housing part number, but the kit number. Oddly enough, if you find the kits, all the separate parts are listed as "related". Go figure.
The terminals are a horse of a different color. I found what I need by matching the Reapir Manual specs against their terminal specs. There are no Toyota part numbers that I'm aware of for the terminals.
The staff are really good about answering emails and phone calls and can find things that don't show up on the site, if they have them, or can get them.
The only connector housing I've asked them for, which they could not find, was the engine harness-side connector for the A/C cutoff switch, in the head. They told me Sumitomo says it's NLA. I did find that Toyota used it on all the 6 cylinders in the 90s, so that may be an option. I haven't pursued it, because I found seals which would fit mine and jammed it back in place (the latch on mine is FUBAR). I'm waiting for it to fail so I can fix it properly.