If you are drilling on "steep" slopes, I assume you will be encountering bedrock, of varying hardness, at some depth. A geoprobe or tripod rig will be of no help, they are intended for softer materials.
You will most likely need to core. There are rigs available, but they are few and far between and pricey. As a start, I suggest talking to some of the bigger exploratory drilling companies out there. Ruen Drilling and Cascade are a few that come to mind.