We bought ours at Sam's Club about three years ago and I want to say it was between 150-200. I could not tell you the brand but I think it was the only one they carried. I think the brands are very similar in quality, the big issue is the thickness. I have seen some toppers that are only 1in. the one we have is 3-4in thick. My biggest complaint is that it will not stay put on the bed, it is very bad to slide off the matteress. My mother in law had a 100% foam matteress for decades & that thing looked and felt brand new. I have no idea what the brand was but it had held up very very well.
You might try overstock.com.