Full Mini Slip Wanted...apply inside

Okay, here's a random (but important...at least for me) question. Where in the world can I get a full mini slip? I have a really cute mini dress which I purchased from H&M. But it's kind of sheer, so I have been in search of a full mini slip. I have been to countless stores and searched countless online stores but to no avail. I now currently own one Gap slip which is ALMOST the right length. If I can' find one soon, I will resort to scissors! Please help me put the shears away!