I am also happy with my cheapo one from amazon.
Ikea do their own one, so I went in there and tested out the different weights. I know about the 10% of body weight recommendation, but I wanted to test this too because there can be quite a difference between e.g. 8%, 10% and 12% of own body weight.
Bear in mind that you can't machine wash a weighted blanket as they would damage the washing machine, I use mine over my duvet so that it does not directly touch me for this reason. Because I was planning to do this I added the weight of my duvet to the weight of the blanket when I was working out which one to get.
You can also get some which have a cover that comes off to wash. If you get one with a cover, it needs to have some way to keep the cover attached to the blanket so that it doesn't slide around inside.