We call them the same thing, or freeze plugs, they rarely leak but it can
happen. An automotive machine shop should be able to help you locate a new
one.

Replacing them is usually done by hammering a tool like a chisel
gently into them and carefully prying them out. Don't drill since
them since you don't want the filings going into the water
passage. Clean the area, look for defects, seal the new plug
and tap it in with a wood block and hammer. The trick is always
getting access to the area.

I'd make a wild guess that plugs have not changed that much in
Saab motors and you can still get a replacement at the dealer.
Also, most auto parts stores carry a selection of them in stock.