The SSS symbol has changed again, hopefully for the last time. It is now ᐁ (you need to have the cueniform font installed on your system to see it). This looks almost like the real symbol, except that in the real symbol, the line extends over the numbers. So if you write ᐁ100, then the line will extend over the "100".
To write the ᐁ symbol in Ubuntu, you can press Ctrl-shift-U and then write 1401 and press Enter.