I believe the strap you are looking for is on eBay at the moment, the part number is 345510. I have one on my 88 with 7.50 wheel on the bonnet with cover. Just adjust strap to fit. Hope that helps.
Is there anybody out there who knows where I can get an oil seal (part no MMPW0400) for a Sankey Trailer MK II BRADLEY over run damper. Also know what oil they use inside? Great to restore one, if I only knew where to get the parts!..