I wouldn't buy an online equivalent for cheaper. There have been a few threads on here regarding problems people have had with them. The stardust from Topps you would be fine with or as Whitebeam says a galaxy granite.
mmmm, not sure i totally agree with that statement, yes there are some online stores selling real bad cheap quartz, but there are some selling gulfstone, which is the same tile as stardust.
As long as it's genuine Gulf Stone, that's the phrase you're looking for.
You would have to check with supplier on weight of the Galaxy, it will depend on the thickness.
I was looking online and found these guys do a competitive price
Black Star Galaxy Granite Tiles | Galaxy Granite Floor Tiles - Stone Superstore
Has anyone used them before?