For the antenna bases, Djiti's does a US Antenna Mount Set (35010) in resin that is really complete and includes straight and bent bases. It is really nice and goes for about $10. I prefer 0.020 rod for antennas myself. I heat the tip to mushroom it to represent the antenna safety ball.

There are plenty of other sets too, just check eBay for antenna bases.
For antenna tie downs, I use thin thread. It represents the thin rope they are made out of well. You can also use a small piece of PE scrap for the clip that attaches to the antenna.


There are a bunch of shackle options as well. Both RB Model and Aber do brass shackle sets.
RB set (Abner looks pretty much the same).

There are also a few 3D printed sets on Shapeways. They are just as nice and a bit cheaper for a bunch as compared to just four in the above sets.