One thing that could help is the "string pod."

Mount a tripod plate onto the bottom to hold a section of string (preferably strong twine) about 4-6 feet long. With the string unrolled to the ground, step on it to keep it in place and pull up on the camera. The tension will give you anywhere from 1/3 to 2 stops increase in stability.

The amount that you can increase your shutter time depends on several factors, but I've gotten decent results with it in a pinch.