In article ,
"Tim Steele" writes:
Having trawled through Google's archives it seems that such things were
available from places like B&Q and Homebase years ago and are still
available in the US (Amazon sell a kit made by 3M) but I couldn't find any
reference to anyone selling this stuff now with the exception of DIY
Plastics who are rather expensive.

Anyone know better?

Sorry, don't know if it's still available.
However, a piece I put up 19 years ago (Sellotape brand IIRC) on
the pane of glass over the front door is still there and in perfect
condition. It is completely invisible unless you know it's there.
It is held in place with double sided Sellotape, and was then
shrunk with a hairdrier to pull it tight and remove any ripples.
I took the effort to very thoroughly clean the window and surrounding
paintwork before fitting it, including cleaning the area the double
sided tape sticks to with white spirit. This care seems to have paid
off far more than I ever imagined.

Meanwhile all the rest of the properly double glazed windows in the
house had to be replaced a few years ago.

--
Andrew Gabriel