Well, my weighted blanket is actually thin in comparison to like a quilt or something. I can take a photo sometime tomorrow morning- it's 1:30 a.m right now so I can't turn on a light.
If you do decide you want one, have someone help you gauge the weight by laying them on you one at a time, giving your body time to adjust before the next one is put on. Once you start to feel 'bad', in any way, then give some sort of signal, verbal or otherwise, and then take the blankets that felt good and weigh them.
Generally OT's recommend 10% of the body weight, and at least 1 lb per square foot of extra blanket. Even though I'm 180 lbs, I'm only 5 ft so I went with a 15 lb blanket. I could probably do with a bit more weight, but I have low upper body strength so it's a challenge for me to get it on alone. (That's what the bf is for. X3)
Oh, and I got mine from
www.saltoftheearthweightedgear.com 
I've heard they don't actually make king size blankets, which might not even be a concern for you, but they are the cheapest but still high quality. Mine has already been through the wash because of a tea incident, lol. It's also been lugged around to the park a few times, and it's still in top condition. x3