This is going to be a list of places that you can purchase Toyota wiring harness parts.
Here are the best sources I like to use.
Great on pricing fast shipping, lots of other non-Toyota connectors which help for other things like if you are using Greddy gauges and what not, you can find the connectors here for them. (in my case the solenoid and pressure sensor connectors for the profec e01) Harder to navigate simply because they do have a list of what parts for the supra specifically the parts are used for. Like their tools provide great crimps for me
Another good source for all sorts of connectors. Again not supra specific but have a verity of everything.
Great place supra specific, not a huge selection yet.
Lots of hard to find harness connectors, but very pricey
Good list of commonly used connectors, but not a full list. Mostly JZ specifc
Great selection and lots of crimping tools
Use this site to find the connector part number and who makes it, very handy. Many connectors have the part number on the back but not the full Toyota part number. This will help you find that.
Just found the holy grail of connectors from china, where all these guys get their connectors
Also see this thread.