I might add a fiddle into the mix (not sure though), but the horns are more iffy, since they are, as you pointed out, more used by heralds and on battlefields, as opposed to individual minstrels, and the equipment list is more designed for adventuring PCs than for other characters. However, the existing list of instruments can also be used to give rough estimates to other potential instruments, since you already have samples...
For example, for a fiddle, use the price for a Lute, another stringed instrument. Will take a closer look though...