I have also used tagua nuts quite successfully. $62 for 15 50mm nuts including shipping (ebay, from US) - not sure if you regard this as expensive!
The nuts are fine and turn well, but note that they have a hollow in the centre - so you can make a round object quite easily (I made a light cord pull perhaps 30mm or a bit more across) and no finish is needed - just polish with very fine grit (like a CA finish). You can also slice and stack to get a longer straight section (for a pen for example) but this is a bit fiddly. There are typically cracks radiating from the central hole (it is a seed after all!) but these can be seen as patina! Small pieces fine for inlay.
Good luck!