Yamiya
David Silver Spares
Are two good suppliers.
Be careful with the carbs, save all the stock brass you can, replacements are hard to find and if they are not OEM the quality is sketchy. Most of the time the brass is ok.
Buy Hondaman's book, a must read to keep you out of trouble:
My CB750 book; On Putting Them Back on the Road
Paperback – January 1, 2010
Available on Amazon
Well worth the money
Again, a must read.