@croman, consider companies offering Reaction Injection Molding (RIM) services. Making standard injection molds for plastic is expensive because the material has to withstand great pressures and heat generated by the process, i.e. hardened steel and the costs of machining it. For rubber molds, it is sufficient to use aluminum, but that still requires a lot of work and would be crazy for a piece as big as yours.
Basically, in injection molding the materials are melted and injected at very high pressures into a cavity that contains your shape.
Now, RIM is a technology where the resin (whether plastic or rubber, it doesn't matter - it's usually some formulation of polyurethane or silicone) isn't melted, but comes in two liquid parts which, when mixed, begin to cure to make a plastic or rubber. The thing is that it doesn't require the immense pressures and heat of standard injection molding, so the mold can be made out of an easily machinable material (like tooling or modelling boards, which are used in prototyping cars), coated with a layer that will prevent the liquid resin from bonding to the mold, and injected at a low pressure using a machine that mixes and dispenses resin.
This is a process that is cost-effective at low volumes and it's used in industries where large plastic parts are required in small numbers (note that when I'm saying plastic i mean man-made thermoset or thermoplastic materials, including rubber). So one option would be to make a CAD of the part, then have your designer make a two-part mold of it (making a cavity shaped like the tail in two parts, with a registration mark to make the two halves go together, and sufficient venting holes in strategic places to avoid air entrapment), get it machined in something cheap and choose a thermoset rubber of your liking at a company that has a RIM machine.
Another option would be just ordering the whole thing from such a company if they can make molds.
On the other hand, you should look into hiring a prop maker, because he could just make a reinforced mold out of clay in a big box and fill it with liquid silicone rubber (depending on the standards required in your industry, this can be the cheaper tin-cure or the more expensive platinum-cure). Silicone doesn't bond with almost anything apart from a similar silicone, so you could get 12 casts from a mold no problem. This is even something you could make yourself, but that just takes time and skills.
You might even have a mold machined and give it to a prop artist to make the castings. Whatever you do, consult your decisions with the people that are going to be doing the job - don't get a pile of modeling board and spend 3 grand machining it only to realize later that it's not going to work with the process you've had in mind. Make the mold in CAD first and give it to the manufacturers.
Whew, I hope that this will help you some, if you have any questions regarding this go ahead and ask. When it comes to costs, RIM materials and silicone rubber are far more expensive per pound than thermoplastic rubber (the one for standard injection molding), but you can save big bucks by having a mold that's orders of magnitude less expensive (and you can probably save even more by making the tail hollow using an insert that fits in the mold cavity, that would use less material).
Definitely pay someone to do this for you, but in this case if you know several methods used for making parts like yours you'll have an easier time for sure.
FAKE EDIT: you can also use a very wide range of polyurethane foams with RIM, that may be a good equivalent to rubber and is used for larger parts.
Check out the process in these vids:
(SOOOO 90s)
(such terribad promotional material in this industry, but it gets the point across)