Do you mean replacement for the Imperial version of the Centrotec Installer Set?
That includes wonderful brad-point drill bits 1/8", 1/4"....1/2". I haven't found replacements for these. Festool used to offer the Imperial Centrotec Wood Bits Set 496942, which I presume were the same, but that set dissappeared in 2014. And I don't think the individual drill bits, say 1/2" centrotec, have ever been offered singly. I hope I'm wrong...
Snappy offers Centrotec imperial options for 1/4" and smaller. Nice for pilot holes.