Steve,
I work in a large hobby shop and I can tell you I sell many more items if I have it already on the shelf, the minute that I tell some one that they will have to wait 95%, especially of expensive items. Many say no thanks, because at that moment buyers remorse has already set in. If they have it in hand they will walk up to the cash registrar and pull out their wallet and pay for it, but if they have to think about it that usually kills the deal. The owner of the store that explains it quite well, " You can't sell from an empty cart! ". And the other saying that you have to remember is that "It takes money to make money!".
Two other things to remember is: The first ting is that the average customer that walks through the door is not one of us, meaning that they are not fanatics which to some degree we all are. By this I mean that they don't volunteer their time, they don't donate money (they feel that the money that they paid for the ride is enough), They probably don't have a library of railroad books at home, they don't read message board like we do, they are not modelers, all they are looking for a nice experience, a nice day out with the family and afterwards as they go through the gift shop they are looking for something that they can remember the experience with. The second is that online, or mail order are a completely different kind of customer, they have already thought about this item as either a gift for some one else or a decoration for their own home at this point they know what they want and where to get it.
Now if you are going to make resin castings those can be done in house for very little money. Make the original and mount it on a smooth surface, build temporary dams around the master so the cast rubber that makes the mold will not run every where. Pour in the mold rubber and let cure. Remove the the rubber mold and turn over and let it cure for 24hrs then cast your first resin casting, and to make it look like bronze you can add a bronze metal powder to the resin before you cast the part. Now you let the resin cure and then remove from the mold. You can also use a layer of paint as a mold release, you paint the mold before you pour the casting resin in and when the resin cures it attaches to the paint which will come out of the mold easily. This method has the advantage that the resin attaches much more firmly to the paint than the paint will attach to the resin, you also don't have to wash the release agent off of the casting.
If you use a two part mold IE one with a back you could cast the railroads name in to along with the information that it is a reproduction. It could say something like this "This Reproduction was made by the Wiscasset, Waterville & Farmington Railway Museum, Alna Maine". As to aluminum or bronze you might be able to get a local trade High School to make them for you, when I went through High School in the metal shop was the capability to sand cast both bronze and aluminum. If you do some thing like this all you would have to pay for is the materials that the class use. Most of these type of programs are looking for something like this so that they can teach the whole casting process and as long as it goes to a museum they don't have any problems with it.
Andre