Unfortunately, the US Postal Service doesn’t offer sea mail shipping anymore.
You could try UPS or FedEx but their air rates are rather exorbitant for large international packages and they don’t have sea mail.
You don’t have enough to really justify shipping your own ocean container or even quarter container.
I agree with a commenter that you may find ...
While cycle touring it's common practice to pack your bike up in to a bike box and check it in as luggage on your flight. Most airlines don't charge anything extra for this service, but do check with your airline first.