You can build your own siphon with a couple of pieces of 1/4" tubing and a garden hose if you can't find the original.
The idea is to pump fresh water in at a corner of the tray, enough to make the prints slowly circulate in the tray. Use a big tray, like a 20x24 or something if you have a lot of small prints, or a couple of 16x20s.
Then you want to continuously extract the excess water and dump it out at the same rate as the water flowing in so that you keep an even level of water in the tray (a couple of inches deep).
But if you can find an original tray siphon, that is easier, obviously.