Hi Fabien. None of our add-ons are available for purchase separately. You can normally accomplish the same thing with a little more work than configuring an add-on feed, using one of these two methods:
I’m not aware of any other solutions at this time. Without the Webhooks add-on, the only other method I’m aware of is using the gform_after_submission hook. Or, depending on your service, Zapier may be able to help (available with a Pro license) or there may be a 3rd party add-on which was specifically created for your service.