Imortal,
I had a plain black wide notch rear sight and a tritium night front sight installed on a slide recently by Novak's. You can send in just the slide.
They will have to mill the sights in even though it may have dove-tailed sights on it now because it is a different cut for the Novak's.
If you want a fiber optic front and rear, LPA makes a model that fits into the current dovetails of a MKIII. The model I purchased was TTF 62BN. Got them at Precision Sales Int'l. They were the cheapest I could find. these will fit your BHP if both sights are factory dove-tailed.
Keep in mind that for concealed carry, the fiber optics are not recommended because of the possibility of the tubes being broken. Doesn't happen often but can happen.
There are other sights, but these are the ones I am familiar with. BTW, turn-around time for Novak's is crazy fast. I shipped the slide on a Friday, they received it Monday and called me Tuesday afternoon that it was done.
Hope this helps.