Ed,
I got my stuff at a Michael's Art Supply store in the calligraphy section. I bought a pen nib set (wooden handle with a few removable nibs) and some bottles of ink. I have used the india ink (black, permanent, will clog up a fountain pen) and also white acrylic.
After putting a few coats of tru-oil on the bow, I wrote the bow info, let the ink dry, and then added a couple more coats over the top for extra protection. I think it was on PA that I saw the recommendation for white acrylic on osage so that when the wood ages, the white really looks good, and was more visible than black - I haven't tried this yet, but the pictures looked good.
By the way, I recommend practicing on a piece of scrap wood with a similar finish if you have not used a nib pen. They only take a very light pressure compared to a ball point.
Michael