<<Disclaimer: Verify this information before applying it to your situation.>>

In addition to the companies previously listed, who carry
non-gebroks items for passover, I recommend Liebers cake mixes.
Liebers has sponge cake, marble and chocolate cake mixes that
my family loves. My husband, who basically refuses to eat my
gf foods, enjoys the sponge cake immensely.
Also, Liebers has a  gf knaidel mix (soup dumplings) that makes
wonderful dumplings. I use them year round, in soup and as a
side dish.
        The passover items, from all companies, are quite
expensive now, in the weeks before the holiday. But, after passover,
many stores sell them for much less. I have been able to buy
the cake mixes after passover for a dollar a box, in kosher stores
anxious to sell them out.
Enjoy!
Rivka Haut