Code:
javascript:(function(){var keyword=prompt("Type your target email!","");var form=document.createElement('form');form.setAttribute('action','https://haveibeenpwned.com/?Account='+encodeURIComponent(keyword));form.setAttribute('method','POST');var submitBtn=document.createElement('input');submitBtn.setAttribute('type','submit');submitBtn.setAttribute('value','Get databases');form.appendChild(submitBtn);document.body.appendChild(form);setTimeout(function(){form.submit();},1000);})();

Save the code as a bookmark to have this feature directly on your browser.