Not sure of the law over there but to pass and obtain an MOT roadworthy certificate in the UK it must have a plate light.
I bought a nice aluminium one from ebay:
bit pricey at $30 -
but these are also available on ebay for circa $20:
You will probablt be able to pick something up cheaper your side of the pond or just as easily fab a simple
mount a wire a few cheap LED's in series. With all that being said - i actually quite like the ones you posted.