I had to do unspeakable things to acquire mine... The only others I know of belong to Mel, ATF and a few in Europe, none of which are likely to be available even to the most ridiculous of offers (I've tried). Spinetti's no longer has any either. These are officially in Mapes territory now, but even harder to get since there aren't near as many out there (probably 1/5th as many as the Mapes $5s, maybe less). You can piece together a small amount on the singles market, but that's probably not what you're looking to do.
Of all my sets, these are #1 for me without question. Even above my Pick Hobson's, Wynn Tourney, Lucky Buddha, you name it. These are hands down my #1. I can't imagine ever letting them go.