realcomponents.com has a decent search engine. Just enter the main body of the part number, leaving off any suffixes, and it will often return some inventory listings. No prices, though; you have to ask for quotes, and the numbers you get back will be waaaay up there.
Same with plain old Octopart, for that matter. They are pretty good at returning qualifying part numbers. Still, there have been times when direct searches at the vendors' sites return results that don't show up on Octopart.