The stream tool toolserver.org/~erfgoed/stream/ had disappeared during the Toolserver migration, and had never made it to Git.
Digging deeper into the heritage directory on Toolforge, I discovered a complete archive of the old Toolserver directory. Among lots of things, the stream tool code was in there!
It turns out it was a fork by @Platonides of another tool by @Jdlrobson, polaroiderizer.
I looked into resurrecting it. It relies on some shared PHP library from /home/platonides/public_html/wlm/shared-wlm.php (which I do not have) to infer Category names and country list.
The tool can probably be resurrected if there is interest. I’ll look into adding it to Git, so that others can have a look too.