Yeah, they're a popular item at the moment. Their official site has them, but they're overseas:
If you'd rather wait until PerformancePCs has them in stock, they'll cut the hole in the top of the case for you and mount it for a reasonable price. I had them do that with my case when I got it there.
To drain w/ a res, you can either have a drain valve at the bottom of your loop or just do what I do and pull the res/tubing out of the case and low enough to drain it into a pan. Then tilt the case to get all the liquid out.
I have no problem draining mine at all, but I do have a little extra tubing on it which allows me to take it out of my drive bay and lower it outside the case so that it's at the lowest point.