On one have got some neoprene ones on offer right now. 9.99. It’s snip, it’s steal etc etc.
http://www.planet-x-bikes.co.uk/i/q/CLPXOSH/planet_x_neoprene_overshoes
I’m with this guy ^ – so cheap, so easy to put on/take off (zips and all that are a ballache and the point at which they’re guaranteed to fail eventually).
If you want more spangly, check out Gripgrab available from wiggle, the reviews are very good. But honestly, those PX jobs are so effective.
Forgot to add, having plenty of room in the shoe for winter socks and wriggle room is a vital component of keeping feet warm – if you don’t’ already have any, buy some cheap shoes a size up from your normal.