I now have the 1.25" 2x barlow (thanks Rob) and - GREAT! The barlow lens unscrews to a small compact assembly which fits the filter thread on the diagonal. Then that fits neatly into the focusser. With the Galileoscope plossl in the diagonal, I was able to reach focus on a light some 400-500m away with about 2.5cm of in-travel left in the focusser draw tube! This looks promising.
