Does anybody have any sugestions as to where i might find a
replacement leaf spring for an old box trailer?

or perhaps a site that lists all leaf spring measurements so that i
can see if they match some sort of car?

I have been offered a free trailer but when went to pick it up found
that a spring is broken. Am trying to see if it is feasable to repair
it or if it would be cheaper to either buy a different second hand one
or replace the leaves with the indespension type units which i can
easily buy.

I am looking for a spring 1.5 inches wide, 18 inches from bolt centre
to centre with a radius in the centre or around 6 inches