Congrats on the good scoop!
For a 40 gal, if you have a sturdy coffee table that would work well (if you and someone else can sit on it, it'll be strong enough).
Other than that, many pet stores sell aquarium stands, but they could be expensive.
And there's always the good ol' cinderblock and plywood solution.
Since it's 12x38 footprint, you could get away with one 8x8x16 cinderblock on each side, and stack it two, maybe 3 blocks high, and put a piece of scrap plywood on the top. You can also put a piece under the blocks, so weight is distributed evenly, and so the blocks don't leave an impression on the floor.
Finally, under the tank, you might want to put something like a thin piece of styrofoam or cardbord, just in case your stand isn't even
