Have a word with David Williams at Resurgam
Resurgam Rolling Stock He used a contract supplier to do his initial ply and MDF cutting a couple of years ago when he started out. He showed his first offerings on their stand at the Warley NEC show 2-3 years ago. They really know how to do cutting. Perhaps they will be able to do the job for you too.
If you are wanting brass then you will probably be looking at a photo etching process rather than laser cutting. Photo etching allows much finer detail to be incorporated including engraved paneling overlays insitu and suchlike. My old supplier Photo Etch Consultants
Home are still going strong. All you would need is to draw a the part (following a few simple conventions, they could even do it for you) x 2 actual size and a prototype tool (photographic film plate) could be made up for a one off. There is very helpful guy there (name escapes me right now) in their design department). I only contacted them a couple of weeks ago to talk about a job II was thinking of doing. They do up to 0.9 mm thickness of material, and not just brass.
However, as mentioned above, all this costs. But worth a look, especially if you are gong to use this as a means of making standardized parts that you will be making a number of tram variants from..... or selling ! Max