John:

The one I got has the same characteristics as yours. I made a square base from 1/4 ply and used industrial velcro to attach the spray bottle. Keeps it from tipping so the leak at the top isn't an issue.

Looks like there has been a "re-engineering" on this bottle as the LHS has some new ones with a blue spray head rather than the red spray head. This has apparently fixed the leaking top (the spray head actually screws on tight) but the ones I looked at still had the "not quite flat" bottom.

I like mine however and since it doesn't tip over any more it doesn't leak.

Dan