Hopefully I got your bike right...
VintageCB750 sells kits individually at a good price
4-into-1 has a full set for $107
Randakk's seems to have some popularity among members here but their set is $180
Both VintageCB750 and 4-into-1 replied to my questions very fast, and their service was good.
My advice is absolutely stay away from the no-name carb. rebuild kits on Amazon. I had to send mine back because the holes in the jets were smaller than OEM, and not all the parts were there.