Economical source of thin white plastic needed

Hi. I have a need for a quantity of white plastic.
Ideal thickness about 1mm thick.
Ideal width would be about 25mm.
I need several hundred meters, I think.

It could be a tape, or might come as sheets in which case I would cut it into strips. If it is sheets, the sheets should be at least 2 meters long otherwise I get too many joins. If it’s a tape, it would need to be rigid enough for 10mm of it to stand up on its own.

What this is to be used for is to fix to the top of flush mounted skirting boards in a timber version of shadowline skirting boards. For those who don’t know, shadowline skirting boards look like this:

Intrim 800 Series Shadowline System | Architecture & Design


This is usually achieved with a P50 bead. I believe I can do it better and quicker by just using an ordinary stopping bead and fixing the plastic to the back of the skirting board such that it takes up the gap usually occupied by the leg of the p50.

I want it to be white so I don’t have to paint it, ever. It will be recessed and very difficult to paint..
I want it to be thin so I can staple some to the top of the skirting board without affecting how the skirting lies.

I’m all out of ideas on where I can source this. Anyone have any ideas?

Thanks
Arron

Maybe try these local manufactures of PVC strip rolls?
PVC Rolls | Melbourne | M.T.I.Qualos Pty Ltd

There was a google hit for a UK supplier.
White PVC Rolls (50m) - Redwood PVC