Boy I looked through my kobolds, and I have dozens, and no musicians. The closest I found was a pig orc musician from the old minifigs line that thanks to scale creep and poor sculpting now passes as a kobold.
I hate to say it but converting will be your best bet. Fortunately its easy to put a drum (a skull with the top filed flat works best) in front of a spearman and clip half of the spear off. If you need straps just cut one or two lengths of paper and soak them in white glue before putting them around the figure.
Good luck