Many more NG locomotives were built without outside counterweights than with them. As the other guys are hinting to the normal practice was to have the counterbalance weights incorporated into the wheel casting (or attached to it) as in Standard gauge practice. It was cheaper, however, with standard parts, to separately add the counterweights on the outside crank pin on outside framers.
I do not know of any twins to the 2-8-0s but Baldwin built many thousands of NG locomotives for export. Earlier outside framed engines had on outside counterweights. Some of these export locomotives survive overseas (or copies). The most wellknown are the 2-6-2Ts built for the 30'' gauge Victorian (Australia) Railways branches. Six of these locomotive are still with us on the Puffing Billy Railway near Melbourne, including one of the original 4 Baldwins. Four (7,8,12,14A) are operational now and 6A is due for completion of restoration in the next few years. The Baldwin, 3A, is a long term project!
www.pbr.org.au