Hi,
The numbers on your outboard aren't going to be of much help anymore. The link to boats.net that eneusiis sent you is the best source there is left for both price and availability of new parts for these old gals. They offer exactly the same as you would find at at any Honda dealer but less expensive.
You will find many parts are listed as "obsolete" but they may still be available as replacements for later models. For example, the pre-97 8hp parts listing will have a few items that will work on an old B100 or B75 even though their listings say obsolete.
Lots and lots of these (B models) still "out there" so looking for and buying a parts motor is not too hard. Then, there is always ebay.
Good luck.