Light sapphire, color of blue zircon!

So I am in the middle of setting one of my custom projects, and I
allowed myself to become distracted for a moment. I push a little too
hard and shov e the sapphire into the diamond that has already been
set in the spot next to it. I hear a little snick and double check to
verify what I already know has happened before uttering a rather
unladylike phrase very loudly. The sapphire now has a tiny chip.

I need a 4.5 mm gem, round brilliant cut, TOP QUALITY. It needs to
look fairly close to the shade of blue zircon used in the birthstone
sets. A hai r smaller than 4.5 might be OK as the other sapphires are
dark blue and the lighter stone would have the optical illusion of
being slightly larger. I know that I can get 4.25 mm from Stuller as
they supplied the original gem, but feel that 4.25 may be a little
too much smaller.

Anyone out there have any ideas?

Mary Latterman