To follow on from Eddies advice, I have checked with the Douglas Club spares section, they do have the front stands in stock together with the mounting bolts and spring clip.
I have to agree with him regarding the Douglas rear carrier, you may be able to pick one up, or even make one from the spec we have, however they are not particularly useful, Ed's observations are spot on, many people fitted proprietary carriers onto the lifting handles, Craven etc, these can be picked up at autojumbles, saw one at Banbury on Sunday! But this does put a load onto the lifting handles which I have known to break off at the weld. My suggestion is to build your own one on lines similar to Douglas but more sturdy and a more useful platform, I notice you are based in London, I have a very good carrier on my Dragonfly (not built by me I hasten to add!) and if you would like to drop in and see (measure) it up you would be more than welcome. If so please contact me directly on via my email, I am based near Ongar in Essex.