What size brace do you have, and what size hole do you want to bore? For the most part, I think I would agree with Phil on this. If you have an 8″ brace, it would be difficult to bore a 1 1/2″ hole. If you had a 12″ brace would be easier. The chuck on the brace will also make a difference. Some won’t hold the bit. I usually forstner bits in my drill press, when it is possible. But to answer your question here are some places.
You can also buy them locally. They have some quality bits at Menards and Home Depot as well.