Well no numbers but you should be able to put on a bar from any 77/78 and probably all years and it should be fine. Like I said, no numbers but that opens up a wider range of replacement options.
However, I did find this:
http://www.vintagecb750.com/search/?q=handlebarAbout 2/3rds down the page. There are 2 listed as being close to stock for 69-71 and 72. You could probably get something close to 1972 and be close to your bike.
Your old bars get bent? You should still be able to measure the rise and general pullback.
If I find any other numbers, I'll let you know.
EDIT, my manual lists the 1977K to have a bar width of 31.5 inches. I am pretty sure my bars are stock and to me, they seem to be close to the 69-71 bars. If I didn't have to have my bike in storage to make room for cars and snowblower, I would measure my bars.
The ride IS the adventure. The destination is just to get gas!