Many of us build our own darkroom sinks (sink = Waschbecken/Becken/-becken) out of plywood. There are lots of designs, but all you really need is a rectangular box with a drain at one end (make sure you tilt the sink a bit toward the drain corner
) and some legs. Heck, you could even just set it on a table. The problems with individual sinks would be that it's awkward to move things around and you can easily drip between sinks.
My darkroom sink is 3 meters by 1 meter with storage underneath and cost me just a few hundred dollars. Even with Germany's more expensive materials, you should be able to build something that would fit your space exactly and work really well for a few hundred Euros.
You need plywood, glue, screws, saw and screwdrivers and some marine paint and your set.
Have fun,
Doremus