Often overlooked when maintaining brake systems, if the head of the bleed nipple is starting to round it is best to replace it. Many older bikes would also benefit from new bleed nipples as you will tend to find they will shear off and leave the thread in the caliper. This is usually because the bolt has seized and is generally now also fatigued from the many occasions bleeding the brakes in the past. 

We can generally supply steel, stainless and titanium options in most sizes with bleed nipple covers too. If you cant find what your looking for just ask.