I'm in need of some door clip replacements, the black ones that support the interior door panel. 

 

They're square/L shaped ones, all I can find online are small round push clips?

I think there might be two types of clip, depending on position on the door.  Search for part number 1U0 867 260.

I've sourced these on skoda-parts.com previously.

I've had good dealings with the following company - https://www.vehicleclips.co.uk/ ususally just type reg in or select make, model & spec etc and will normally give options for nearly every clip on the car!

The part numbers are -

 

1U0867260C - side of trim clips

1U0867260D - base of trim clips

 

They are about a fiver each from the dealer, if you can't find a pattern part with a part number search