I think that while the gruesome details are very important to the song, so long as they remain gruesome any details will do.
I've heard the song sung where it is the hair used for the harp, where the fingers are used, where the breastbone is used. I think the strongest tradition is probably the golden hair of the fair sister. This works as a visual image but I dont think you could weave it to actually make it work.
Guts, intestines, have often been the sources for strings, cat guts mostly.
Alternately, any skin can be stretched and tanned for a drum.
Bo More Gross than he wants to be.