Fresnel Screen

Hi all.
On a previous motorhome I installed a fresnel screen to the rear window to improve the rearward vision. As I recall I bought the screen from an advert in one of the motorhome magazines.
Now that I have come back into the fold from touring caravans I wish to equipe my Exexutive in a similar way.
Despite looking in the mags and going online I have been unable to locate a supplier.
Can anyone offer any help with a source of supply.
Many Thanks,
Mick.

Can't say I've heard of this screen, what did it do, give wider vision like the reversing lenses that are available?

Edit - Having just googled 'fresnel screen' it appears that I was thinking of the right thing. There are some on Ebay here -

http://www.ebay.co.uk/itm/Motorhome-Camper-Van-Rear-Window-Lens-Reversing-9x7-/280702988547?pt=UK_Campervan_Caravan_Accessories&hash=item415b33b103

there are plenty on there in various sizes.

Hi Paul.
Yes. The screen gives a very wide angle view of the area immediately behind the 'van. Very useful when reversing or to see who is driving too close to be seen in the rear view mirrors.
I do believe I am correct in calling it a fresnel screen. At your suggestion I typed Reversing lenses into Google and found myself in Photographic territory, so thanks for your reply but we both await a more definitive reply.
Cheers.
Mick.

Sorry Paul, my last post crossed with yours. Thanks for the link. I will have a look.
Mick.

Hi Mick,
Last time that I bought one, I got it from Halfords, also Motor world used to stock them.
Pete

Thanks Pete.
I spent ages trying to locate a source of supply. Finally the hilary part of micknhilay located a seller on ebay. Job done.
Cheers.
Mick,