David wrote:
A 50 mm x 50 mm sample of 1 mm perspex might just be big enough, and at
£1.50 post free could be worth a punt.

1mm perspex is very weak - I wouldn't want to use it for anything
structural. You'd probably want to look at 3-4mm minimum, but note that it
fractures easily. I wouldn't use it for your application - metal is better.

http://www.mackay.co.uk/metals-warehouse.html
is our local metals place - they will cut and mail order, but you might also
use the catalogue to find what sort of thing you want.

Theo