If your making lots of vegitation, then Woodland Scenic make lots of good tree kits and stuff you can use for shrubs bushes etc.
If you are only going to make a few then look out for Scale Link products. They make a range based on model railway items but include photoetched leaves/branches for trees that can be attached to a trunk of your coice or can supply white metal tree kits for these. The range I have seen mainly covers European subjects but they also include palm leaves in their range. They also supply in photoetch various leaf forms such as pond plants reeds and garden/scrub plants. I must admit that these items are not cheap but I would rather use them over any other product that I know and have done on several professional commissions.
As to suppliers try model railway shops or suppliers to architectural modellers.
ON THE BENCH
Dragon Bachem Natter
Hobbycraft 109G10 Croatian
Scratchbuilds
FW Flitzer
Me262W
Me262P.98
I might be old but I`m ready and full o`piss and vinegar.....................mind you this mornin` it was jus` vinegar