2007 suzuki reno transmission fluid change?

I have a 2007 suzuki reno that i would like to change the transmission fluid on. From what I have read, it is a simple drain and fill procedure. Procuring the parts for the job is another matter. I first need a 8mm or 5/16 male pipe plug adapter, I have searched everywhere to no avail. Any ideas where I can buy one of these? Also, the fluid is supposed to be a Esso Lt 71141 fluid. I have had several different fluids cross matched but none seem to be the exact product. The Esso is about 20 dollars a quart but all the fluids suggested to me seem to be around 6-7 a quart maximum. I cannot find the esso oil anywhere online or in town. any clues? Ive heard everything from castrol import to toyota fluid. The transmission is still under warranty and I want to ensure its not voided by a simple fluid issue.