Personally, I use SlickDeal's notification system since people are all over the place finding stuff like this and you can customize it in all kinds of ways. In other words, let others do the work
You can also sign up for alerts at deals.ebay.com but I think it sends you an email with all the "new" daily deals.
Pentax stuff is posted so rarely I don't have an alert set up. I actually found the deal here on PF then went to SD to check it out further.
Edit: Beach's best promos are almost always Daily Deals on ebay.