For spark plugs, HT leads, terminals and allied spares google The Green Spark Plug Company Ltd. Tim Green attends several major auto-jumbles and has a mail order service and is able to provide all old bike as well as modern vehicle ignition spares. Following the advice given earlier there are no known manufacturers or suppliers of inlet manifolds or exhaust sytems for 2.3/4hp models. These items occasionally appear on ebay or with luck you may get a response from this Forum. Neither item is beyond the capabilities of a reasonable mechanic to manufacture from scratch. For members of the LDMCC, the spares scheme used to stock the lock rings used on both inlet and exhaust manifolds to secure to the cylinders. I cannot say whether these are currently in stock. Chris.