OT: Tool Question - Triangle vibrating tool / sander gizmo ?

[cbelt3]

As part of our inlaw house to be sold cleanup, we've got a lot of wooden windowsills that need to be sanded and re-varnished or polyurethaned. My father in law had a "Fein" tool that worked exceptionally well, but... it looks like he loaned or sold it to someone before he died, so we don' t have it any more. So I need to buy one.

And now there are a lot of copies of that sort of tool. Does anyone have one they like ? It will probably get lots of work, so a cheap Harbor Freight model would die.