I have bought a few plants off of Amazon/Ebay including a listing from AquaticArts with what is easily the largest portion of Java Moss I've gotten off of Amazon. Currently it is out of stock though.
I also recently bought Salvinia Minima and Red Root Floaters from a seller on Amazon which shipped from New York and made it to me in California perfectly fine after 4 days. It did have a small snail on one of the plants and there was a small worm in one of the bags but I just took the snail off and tossed it in a jar I've got seed shrimp living in. After a good dip in dechlorinated water and thoroughly inspecting all the plants I couldn't find anything else.
So if you have to order online it is definitely a viable option, even from unknown Amazon/Ebay sellers.
Another option is the Craigslist/Facebook market place as there may be someone near you selling it. And as has been mentioned /r/AquaSwap is another choice if you want to buy from other keepers directly.
Someone in your /r/fishtanks post recommended you get live plants. This is a good recommendation but you were right, plants can be harder to get right than fish, and it can add unwanted complications if you don't know what you're doing.
He recommended Java Ferns, which are hardy, low light tolerant plants, but depending on your water they will still not grow. We need to know more about your water to know what plants you can grow, but usually a safe and easy "beginner plant" is actually Java Moss. Java moss is tolerant of low light, low nutrients, and just about everything else. It's a good "filter plant" for your tank, and it will work with the light you have.
[Edit: alternatively, if you can come by "Duckweed" which is illegal to import in a lot of places, it's a miracle plant when it comes to filtering your tank water. It is messy and you'll have to clean it out of your tank every now and then, but it floats on the surface so it's pretty easy to manage in a small tank. It's illegal to import in some places because it grows so fast and is so hard to kill that it can take over ponds, streams, lakes, etc. so you need to be careful when you clean it out of your tank that you dispose of it safely. Don't flush it down the sink, toilet, or bath tub. It is not illegal to own, at least in the U.S. ]