Amazon Search with [H]ard|Forum referral code

In Firefox, click your Search box's site icon. In the resulting dropdown, you should see your existing search engines at the top and an option to manage your search engines at the bottom. Between those, this page should also give you US, CA, and UK options for adding an Amazon [H] search engine. Simply click the appropriate one and you should have a new search entry for Amazon which includes the [H]ard|Forum referral link.