I have a set of bits and I borrowed one from CRW reef because I didn't have that size you can borrow the ones I have or if he doesn't mind since I have been super slacking and haven't gotten his back yet you can borrow his
I bought my bit on Amazon, was $6 with 2 day prime shipping. If you know the size you need just type in "diamond drill bit 42mm" or what ever mm size you need. Handy chart from Bulk Reef Supply (I've used regular ABS bulkheads, not the HD Schedule 80):
30mm Glass Drill bit works with our 1/2" ABS Bulkheads. 35mm Glass Drill bit works with our 3/4" ABS Bulkheads. 42mm Glass Drill bit works with our 3/4" heavy duty SCH 80 Bulkheads. 45mm Glass Drill bit works with our 1" ABS Bulkheads. 48mm Glass Drill bit works with our 1" heavy duty SCH 80 Bulkheads. 60mm Glass Drill bit works with our 1.5" ABS Bulkheads. 65mm Glass Drill bit works with our 1.5" heavy duty SCH 80 Bulkheads. 75mm Glass Drill bit works with our 2" ABS Bulkheads. 85mm Glass Drill bit works with our 2" Heavy Duty SCH 80 Bulkheads.