My favorite scratch pad is a simple bookmarklet:

"data:text/html, <textarea style="font-size: 1.2em; width: 100%; height: 100%; border: none; outline: none" autofocus></textarea><script>window.onbeforeunload = function(e) { return 'really close?'; };</script>"

Keep it open as long as you need, and it prompts to confirm before you close it.