Overhead bins will fit a small carry-on that is 9 inches wide and 13 inches deep (typically will be a 17 or 18 inch length carry-on). Example is Swissgear 17 inch 2 wheel model 6283. External dimensions are about 18 x 9 x 13.

Smallest overheads are Embrarer 145s and 200s but the bag size above will fit. Bins are a bit bigger on CRJ-700 or 900. ERJ-175 I think standard carry-on will fit.

If you go this route note that it's helpful to carry the bag rather than rolling as you approach the gate, as agents will typically want to valet check anything that rolls. Don't overstuff the bag as the fit (depth) will be tight.