When I decided to put socket cap bolts on my bike, I used the parts manual and built my own list of bolts to buy. Then I went down to my local fastener shop (Brafasco here in Southern Ontario) and bought the lot.
When the exact size wasn't available, I went for the closest smaller size, so long as it was pretty close. Alternatively, you could grind a longer bolt down to the spec size from your parts manual.
For critical bolts like the ones you mention, it might be better to simply order new ones from Honda. Granted, they may be phillips heads, but how often do you remove those particular bolts anyhow? New bolts will still look nice, even Phillips.