i like all of those. i may try setting mine more in the ground. right now i have one of the roll around kind with the wheels removed, sitting on landscaping bricks.
you didn't say how big an area you wanted to cover. mine is just sitting on 8"x16" pavers. about the cheapest pavers there are, and probaly most common too. i got mine from a couple different places when i saw them at good prices, and even used off craigslist a couple times. being so common they all match, except a bit of aging difference, which was ok by me. i just added them as i got them 'til i had what i wanted. if you did the trick where you spread them apart to let grass grow bettween them, it would take even fewer to cover an area.
edit to throw in a pic
i'd kinda forgotten what i did. it's not really on the pavers, they surround it. i also remember why i didn't put it in the ground (the pond liner. any new fires will probaly need to be pretty small too). they stop on one side because it's supposed to turn to mulch, but just now looking at it, i may add a few more so mulch doesn't come right up to the fire (guess i'd dampen the mulch down first anyway).
the red pavers were another cheapish find i couldn't pass up, so i got enough to work into a pattern, which let me also pull up a few of the grey ones and stretch the area out a little more.
like the op, i almost never use the pit. i just liked adding it to the outdoor idea. the investment was small enough that i don't regret it.