Today I took a new CZ Safari in .375 down to a friend to try out. He really liked the rifle, but had problems with the size of the front sight. Is there a "drop-in" replacement with a somewhat larger bead available?

Not that I know of it. I have made several large bead sights out of NECG's front sights without any problems. These sights should have a lot of meat for you to file them down to fit CZ's sight base. You will probably have to reblue the blade after filing and fitting to make it look nice and for protection. NECG told me sometime last year that they were gonna try to have some made from Germany specifically for the CZs but I don't know if it has happened yet. It does not hurt to call them to check it out. Good luck.

Ditto. I've looked and have yet to find any replacements.