This is happening in the "for sale" section, and it will fit GXs too!
http://www.toyota-4runner.org/sale-t...2A-2015-a.html
Beyond Cargo Slider for 4Runners/GX460 (all gens)
- with 3rd row seats
- without OEM slider
Group buy deal: $400 shipped (or to the manufacturer/dealer, or even you can see it as $300 + shipping)
The unit retail for $499, lowest price I can find anywhere else is $399 (close out, with few units left); PLUS $100 to $150 shipping due to the size/weight of the part (member had reported paying $115 for just shipping). I have looked at similar products out there (truck bed trays, much more expensive) and OEM solution (probably $1500 worth of parts, have to be order piece by piece); and seemingly, this is the best - cost, flexibility (in & out), and it being no perm install needed. By the way, this is going to be similar to, if not cheaper than, just a dedicated slider for a fridge!!
For more pics & info for the install, please take a look at this thread:
Beyond Cargo sliding cargo tray