I'd say not to buy one but to find out where you get buy/borrow or hire one at late notice.
:yeahthat: Exactly what I was going to say.

When DS2 was 4 days old, we made an emergency dash to the chemist; my milk was in & he couldn't attach. I had to express before I could feed him. Luckily they had one there so not too much of a drama.
With DD2 I bought a pump ahead of time, being prepared; but due to other issues we have ended up fulltime expressing. I never used the pump I originally bought but ended up with a different, 'super-dooper' pump.

So IMHO the best bet is to make sure you can get one at short notice if you need to, then wait & see ...
HTH