MK3 Octavia - Sat Nav Upgrade

Hi All,

I'm a long time Vag Owner having had a Mk4 PD130 Bolf, BTCC PD140 and a TFSI Jetta (current car). New job means I need a derv again and I'm looking for a MK3 Octavia VRS. One thing I am struggling with is the Sat Nav Options. Most I look at have a quite small screen and having mates with Golf R's and Pro Nav I was wondering if it was possible to retrofit a bigger satnav if I can find one? Alternatively if you have one how do you find the screen?

I was looking for a how to guide but the lack of them is making me think its not an option.