Someone at the osCommerce forum posted for a way to manually create a customer account in osCommerce 2.3.1. A similar addon does already exist for older versions of osCommerce, but the code leaves a bit to be desired.
Step 1. Create the “Add A Customer” form to the admin
– copied the create_account.php page from the shop side and made a few changes to suit the differences in code between “shop” and “admin” files. Also ported over any included files (such as form_check.js)
– removed some of the un-needed code from the file
– amended other files to suit (filenames.php, language files and so on)
Step 2. Add the link to the new page into the customers infobox
And here it is in action;
This will be released into the osCommerce App Store when it opens to the public, until then it is available directly from me as a commercial addon, priced to suit your site (including installation).