I just went through this. When I bought my bike, it only came with one key. I put it someplace "safe" and forgot where that was.
Depending on your model and year, you may be able to have a key cut by the code that may be stamped on your locks. My bike is a 77 750f. On it, there is a number stamped on the outside of the lock cylinder. It is very small. I pretty much had to take it off to read it. I think there were 5 or 6 digits there - only 3 mattered. I took it to my neighborhood locksmith (older guy who knows his $hit). I already knew the key blank type, but he didn't need it I don't think. He just looked up the code and cut a key. Cost me $20 for the first key and $5 for a copy.
At some point thieves got wise to the codes being on the locks and Honda stopped stamping the lock with a code. Locksmith said all he could do if that were the case is pick the lock. That service is by the hour and costs $$
A key (pun intended) bit of advice from the locksmith was that all owners should write their lock codes on their title for future reference if needed. If I had known my key code and blank type, he could have cut a key without having the lock.
I learned what key blank I needed from the guy at this website. http://www.hondakeys.com/key_id.html
He also caries some NOS keys that are already cut if you can find your code. He didn't happen to have one of my keys in stock.
Hope that's helpful.