I've gone 2 different directions with my harnesses - but the main backup cam connection was done using one of these:
Axxess AX-TOYCAM-3 - Add-On Harness for retaining OEM Backup Camera (includes 12-6v stepdown?)
Metra Online
I found for $9.49 on Ebay, though I only see this one from BestBuy now for $20
Metra Harness for Most 2011 2014 Toyota Vehicles Multi | eBay
It's a 24 pin harness that connects to the one in your RAV. It has both male and female 24 pin connectors (female doesn't connect to anything), and has male and female RCA jacks that support either the OEM camera or allow you to add a 3rd party one. The only thing it's missing is Reverse wire that comes off of pin2 on your 28-pin connector.
My first harness - which was pieced together from a few different ones - included an ASWC1 controller (~$47), and an Axxess AX-TOY28SWC add-On Harness with RCA Audio In - $6.99
Amazon.com: Axxess AX-TOY28SWC Steering Wheel Controller Add-On Harness with RCA and 28-Pin Connector for Toyota Vehicles: Car Electronics
The TOY28SWC had a free Reverse wire coming from Pin2 on it's 28pin connector - so I just connected to the Head Unit's reverse pin, and connected Yellow and Black wires from the AX-TOYCAM-3 to the Yellow and Black wires in my main harness.
Everything worked - including the backup cam, though I wasn't getting all of my SWC keys.
I spoke to Pumpkin support, who said I actually didn't need the ASWC1, and said they had a Toyota-specific harness for $18. I bought it (10 days to ship), and it was a nice, simple harness that connected SWC directly (no controller), but it didn't have a pin in the 28 pin connector for the reverse wire (they told me this before I purchased). See first image attachment.
The pins mentioned in the previous comment 'do' fit this 28 pin connector, so I soldered a wire to one and carefully added it at the pin 2 position. You want to be careful if you do this, as once you get it in place, you need some special tools to even attempt to remove the pin. But it worked as expected (see second attachment)
With the pin added, everything works with the Pumpkin harness - including the OEM camera - though I'm still using the AX-TOYCAM-3 24 pin cable with this setup.
In this configuration, you 'only' need the Pumpkin harness and the AX-TOYCAM-3, but I had to add the extra reverse wire, and I also had to cut the yellow and black wires on the Pumpkin harness, so I could splice in the yellow and black wires from the AX-TOYCAM-3.
But - I'm still not done yet...
One issue I still have is that the Pumpkin harness is only allowing the head unit to see 4 of my SWC keys (Pumpkin support tells me that I should see ALL of them, so we're still working through). With the ASWC1 setup, I was able to see 8 (out of 12) keys.
