One source is a craft market on the outskirts of Bolga, but there is also a place referred to as the basket market, which is less of a market than a dark, unenhanced room with baskets piled in it. We went to both but it was the latter that had much more greater choice and higher quality for what we were looking for.  Laura went wild.
Bolgatanga also has to be counted as a maintenance stop. While Laura was basket shopping I went to deal with the slow leak in the right rear tire, which was actually not so slow anymore and had gone completely flat while we were in Sirigu.  The affable roadside tire guy I chose was quite amused by the hardware he pulled from inside our tire: a 2″ inch nail AND a 3″ bolt!