These are GREAT!, powerful but relatively quiet too.
Pretty sure they would be available in the US as well.
My wife has one, and yes it's very quiet, not sure it would be able to keep vibrating all day though, and not sure how effective it would be if used on the inside, think it's mainly supposed to be a clitoral vibrator, as when i slip it inside my wife she can feel it but only when i stroke her clit does she hit the roof!..have tried it in her arse but she didn't really go for it, she preffers several of my fingers in there instead, which i'm just fine with...obviously!