It's 1-1/4"
drain and need a p-trap that has something like 3" or less distance
center-line to center-line inlet to outlet.

Says he suspects it was supplied w/ the fountain...guess I'll try Halsey
Walker, too, and see if they have an answer...
I think they're Halsey Taylor now.
http://www.halseytaylor.com/index.html
Also, there parts number is 1.800.323.0620