|Paint it to camouflage it or make a flag pole|
Alot of this type of stealth antenna is basically a long telescoping fiberglass tube with a wire in it cut for a certain band of frequencies. Then you use a good antenna tuner to tune the system properly so you don't burn up your ham radio. There are plenty of places on the internet where you can purchase the fiberglass tubing or you can buy one off of ebay. Here is a link below where you can click on to find some good deals on these fiberglass telescoping masts. The wire can be bought off ebay or from your local lowes or home depot store.
CLICK HERE FOR Fiberglass Telescoping Masts And Fiberglass Flag Poles
The other type of vertical stealth antenna and be built out of telescoping aluminum tubing. It can be placed in some heavy duty pvc pipe and disguised as a flagpole. You can even buy some of these fiberglass flag poles to install the aluminum tubing or wire in. Once again ebay is an excellent place to buy these from. Here is a link below where you can search for these items.
CLICK HERE FOR Aluminum Tubing
Refurbished Flagpole by gwaldon85
The above video gives a good picture of what the flagpole would look like. You would never know it was an antenna.