The Supply Store did stock stamps once upon a time. One variety included Ballycumber and the basic text from the free-download labels - no explicit "BCID:" caption, but easy enough to add a BCID beneath it.
Another stamp was designed by the BCinDC folks for the Washington DC convention; they gave 'em out in the welcome bags, and very nice they are. They have a very simple caption, just the site URL, "visit this book's online journal", and "BCID:", and are small enough to use even on crowded title-pages. (I mainly use mine to stamp the book's *last* page, or the first page of the index for non-fiction, as a reminder to the reader to journal the book if they didn't do it before they read it. I hand-write the BCID beneath the stamp.)
I've made my own stamp, too, one that I use on title-pages; it's a standard office-supply-store customizable stamp, three lines of text, and I managed to squeeze in the site URL plus "Where's this book been?" and "Read, Enjoy, Release!" Again, I write the BCID beneath it.
*And* there's a plain old rubber stamp, circular, with Ballycumber in the middle and the site URL around the edge - that one doesn't come with a built-in inkpad the way the others do. I have one of those, too, but don't use it as often as the rest - but it might make a nice alternative to a sticker for use on the outside covers of books. Hmmm, maybe I'll dig it out and experiment with it - though it wouldn't show up on dark covers, and might not stick well to glossy ones. Worth a shot!
I use bookplates - the free-download ones as well as the supply-store ones - on the inside front covers of my books, as they contain more info than most of the stamps and are a bit more eye-catching. But one could use markers to hand-color parts of a stamped design - a quick yellow dab inside the body of a Ballycumber might be enough to draw the eye.