For a one-time molding, I second Instamold and greenstuff. They should cost around 15 $, no more, and likely less. They're not perfect, and you're sure to make a couple of failed tries. But they don't require the learning of the whole moldmaking process, nor the investment in the equipment. Of course, any moldmaking, even with instamold, takes some time.
Eventually, you ask what is the best cost x time method for you to get those 50 heads.
If you're really unsure about the molds, a trip through the free market might help. It seems that today the Pistolier heads sell at 1.50 $ apiece in the eBay, plus postage. 75+ $ for 50 heads is definitely too steep, and there aren't that many on offer anyway.
Hoard 'O Bits has them significantly cheaper, and they may be restocking some time in the future. Hawk them.
Now, the box comes with 17 heads (16 if you don't count the bare one), so you want three boxes' worth of heads. Those three boxes cost you 87 $, so from the start on, don't look for individual heads from the web. Unless you can find a bunch, you can buy three boxes just for the heads and sell the rest (with some alternative extra heads). You should be able to get 10...15 $ per box at the minimum, and likely more (because the 9th Age & Kings of War both make the Pistoliers a game choice). That would cut down the cost of heads to no more than 50 $ (still atrocious, and many times higher compared to Hoard 'O Bits).
Compared to instamold, greenstuff and trial & error, you would pay 35 $ more and spend some time in reselling the stuff. Compared to other methods, the cost x time comparison could be more or less beneficial. And you would get exactly what you need, factory made, ready to use.
There's also a chance that if you started to offer tens of dollars for 50 heads, someone on this forum would cut in and offer you the bunch cheaper than eBay or Hoard 'O Bits. Or try getting them piecemeal. I know I have some extras, but i'd bet you will find them on your continent too.
So, how much time & effort will money save you? What is worth what?
(Remember: learning a new hobby skill is tremendous, and always worth the money & time you put into it! Instamold is reusable, and before long, you will find yourself duplicating other bits too. Real moldmaking stuff comes in big bottles, you can do much more after you're ready with those heads.)
-Z