where can I find mounting legs?

Hi,

I finally got my fixture today.
It's a 36" Jebo 2X55W light, but I hit a snag.
It is 36" long but so it's my tank, so the fixture just sits on top of
the tank instead of having the little mounting tabs slide on the side
of the tank to secure and hold in palce the fixture.
So I need some kind of solution for this problem otherwise the fixture
might topple and fall in the tank.

I don't know where I can find mounting legs, so please help me find it,
or provide with some kind of solution that will hold the fixture in
place even if there's an earthquake. (I know I'm exagerating).

Any help is appreciated.
Thanks.