From a manufactures point of view...
Why would I give you a free PSU to review?
The only point of doing it is to sell more units, and you can't help sell because you don't have a website and If you do, you don't have a reputation or enough visitors.
Thats before we even consider the fact you probably don't know how to properly test a PSU.
Create your own website, buy borrow or steal as many current PSUs as you can, along with all the testing hardware.
After a few years, if your website is popular enough and generates enough interest, you can approach manufacturers for samples.
Until then, reviews and review websites are a dime a dozen, and theres loads of competition out there from sites who have been doing this for every piece of computer h/ware for decades.