For that DIY'er in most of us, you can reuse the factory Model Y license plate frame that comes on your car. I like the look of it, and I haven't found an aftermarket one in black that is designed the same way. The one pictured below is from my Model 3, and the paint is well over a year old and has been through rain, sun, and lots of car washes, and it still looks exactly the same.
Just sand the frame to scuff it up with some 400 grit sand paper, and then go over it with some 800 grit to smooth it out, and apply some light coats of satin black paint. Not too bad for about 20 min worth of work and a can of paint (you don't need high temp engine paint, but that's all I had laying around in satin black).