Michael,
Some quick replies/clarifications:
Really Right Stuff, though very important to many professional photographers (and anyone else seeking perfect solutions to complicated yet everyday camera mounting problems that the rest of the industry inexplicably ignores), is a small manufacturer. They are not available in stores anywhere as far as I know. They do direct sales worldwide--here's a page to learn more about international shipping if you are interested.
http://reallyrightstuff.com/rrs/websiteinfo.asp?fc=9
I entirely understand your concern about the price of the products I mentioned. I agree they make no sense for use solely with an ED50. They only make sense if the tripod is being used alternately for camera and scope, in which case the quality of the heads almost makes using a ballhead with a scope bearable, and the quality is "necessary" for camera work anyway.
I can't resist putting in aother plug for the RRS BH-25 (especially the Pro version since it allows for use with a nonrotating AS type QR plate) for anyone looking for a small ballhead. That little head is a bargain in my opinion (and the price is relatively low compared to other RRS heads). It works flawlessly and bears more load than heads that weigh 4+ times as much from other manufacturers. I wasted a lot of money on a progression of little ballheads over the years that were expensive and unsatisfactory (e.g. some from Manfrotto, Gitzo that cost 1/2 the price of the RRS BH-25 but are really only suited to such tasks as aiming off-camera flash units, not camera or scope support) until RRS released the BH-25. It is, by far, the best mini-ballhead ever made.
So again, I'm of the opinion that a lightweight fluid head is a better choice for scope work than a ballhead, and a good one can be much cheaper than a good ball head. Actually, for the ED50, I'd look into finding an old scope head from the days before fluid heads took over the market, you know--the sort that have a single handle for panning and up-down movements and which locks the movements when you twist the handle. That's what I'd use except that I need the ballhead for the camera. These sort of heads can be of very good quality, very light weight and compact, and very very cheap. The place to look for them is a used camera shop that has bins of "junk" tripod accessories etc in the dark corners. These sort of heads are unpopular now because people prefer fluid movement for video and heavy scopes, and they're no good for 35 mm type cameras because they don't allow for turning the camera to the vertical. I have a beautiful one from Slik and another from Bushnell, but I doubt they still make these. Modern ones are likely to be found primarily on very cheap tripods and to be of inferior flimsy plastic design (and probably incorporate a crummy QR-plate and maybe an unnecessary poorly-executed provision for vertical tilt).
--AP