Doubt you'll find that type of mount for what you want to pay except perhaps used. Those were/are also marketed as Pinpoint AM40 (believe they have discontinued selling theirs) and Videoescu side clamping mounts. You could also drill into the speaker cabinet for other options but get one sufficient to hold it in place for the weight of the speaker (and usually they lie about how much weight such other types of mounts will actually hold in place).
"I realize that somebody playing free music isn't as commercial as a hamburger stand. But is it because you can eat a hamburger and hold it in your hand and you can't do that with music? Is it too free to control?" - Don Van Vliet (aka Captain Beefheart) discussing commercial success in the music biz