Which fanplusfriend costume are you looking at, the typical Sokka
or the meteor sword episode Sokka
? Because both of them look pretty accurate-- in fact, they look like the most accurate ATLA costumes from that site outside from Yue's. I have no experience with buying cosplays from websites, though, so for all I know, it could come to your house looking completely different. It's a risk worth taking if you don't have the time or skill to sew it yourself, though.
Also, it's alright to be not entirely accurate, especially if you're new to cosplay. As long as you're recognizable and you're having fun, it's awesome. Cosplay is about having fun
I'm not sure where you'd find his boomerang or meteor sword, but you could probably make them yourself before October 30th if you really went into crunch time (which is what I'm doing with my Katara costume, lol) and had access to the proper tools. Here
are a whole bunch of tutorials, including a cardboard sword if you're really pressed for time.
I hope that helped!