Allan, if you were able to post up more information, boiler make, model, even a few images then someone may have a spare part which the currently use as a door stop which would suit your requirements.
Alan last year I found a damp patch near our back fire boiler, 40 years old, and it seams a fitting which was a screwed in iron elbow was corroded. I called a plumber and I thought he could replace the boiler as heat only back boilers were advertised a couple of years ago but he said they should be kept well clear of. He suggested fitting a new heat only boiler in the loft which used all the original pipework just putting in a couple if pipes to bypass the old boiler and an electric fire in place of the gas back boiler front. The fitting took two days and the biggest hub was fitting the chimney through the roof. The new boiler actually uses less gas cheaper to run and has a seven year full warranty and it is a heat only boiler.