David,
Here is a two step process to get a black plastic bezel for your Nextion display.
First, go to the ITEAD website and down load the 3d bezel zip file for the size of your display and unzip to your desktop.
Go here:?
Next, go to??and?go through their order process that requires that you upload the file from step one above. ?You will need to indicate the color and the material you want to print with. I went with the cheapest and looks great. ?The 3dhub company has great customer service.
Mine cost $9 including postage and took about 10 days. ?Hope this works for you.
