There are a couple of aftermarket auxiliary tanks available - Rouge's link points to one of them - and Toyota made a 50L aux tank that fits in the well above the spare tire carrier.
The OEM tank was very popular in Australia, but never installed on U.S. spec trucks so is difficult to find. There have been many long posts on this subject, so use the search tool and go back about a year and you will find all sorts of useful info.
- You get a toggle for the gas fill to redirect gas to the aux tank from the same fill neck
- You get a switch to install in the dash to show main and aux levels using the existing single fuel gauge in dash.
neat and clean...and a good excuse to get a slee rear bumper for that tire carrier!
For the most part, Dan's comments apply to an aftermarket aux tank installation. The OEM setup is (can be) somewhat different. For the latter case...
1. The tank is smaller, and fits above the spare tire carrier - so you DO NOT have to loose the spare - but the amount of fuel carried is less;
2. If by "toggle" Dan means a dual-filler neck, then yes, there is a Toyota dual-valve neck that is operated by a mechanical lever;
3. OEM aux fuel installations had a second fuel gauge, though you can opt for a single gauge, toggled arrangement as suggested.
As I mentioned previously, finding the OEM parts can be a real hassle. What you end up doing depends upon the application - how much fuel you need to carry - and how much of the OEM setup you would like to retain.
We have Long Ranger tanks in stock (not to be confussed with Long Range Automotive). 44 US Gallons. Goes where the spare used to be. Comes with sending unit and dual filler neck. As for wiring and plumbing, no-one in the US sells a ready to install kit.