Best cage for a Robo pair?

[freyashamsters]

So recently I've been looking for a new cage for my two Robos as my current one is too small. Being young girls, 1cm bar spacing would be too big for them and I don't want to risk it. So I either need a tank style cage or a cage with very narrow bar spacing. I'm looking for a cage under about £50 as I only have £35 saved up and my mum doesn't want to spend more than about £15.