Being a 490, I presume you're somewhere in Europe or the UK. In the
US, most tow trucks carry a device known as a "Slim Jim", basically a
thin, flat piece of steel which is used by sliding it down between
the window and weaterstripping, hooking a cutout in the side of the
Slim Jim onto the door latch mechanism, and pulling or pushing as
appropriate to actuate it.

You may be able to pull the broken-off piece out with a pair of
tweesers or very fine forceps; you should be able to then take the
pieces to a locksmith and get a new key made.

Alternatively, you might be able to take a small piece of wire, put
a drop of super glue on it, and press it against the end of the broken
piece, allowing you to pull it out. Then, off to the locksmith again...

Once you get a good key or the locksets are replaced, make several
spares--the expense is trivial compared to what you're facing now.

Keep one in your wallet, a couple in your house, maybe one at your
office.

Gary