Choosing toroid for FM dipole choke
If you want to choose a ferrite material suitable for the application you MUST look at its complex permeability. This is material 43 (from Fair-rite): -



The picture tells you why it is classed as a good suppression material for frequencies of 20 MHz to 250 MHz - of importance is how the \$\mu ''s\$ graph peaks in this area and how the \$\mu 's\$ graph starts to fall. This means it is very lossy in the region above 10 MHz and is precisely what you want for a suppressor. But not what you really want for a balun at 100 MHz. Yeah it will be adequate but looking further afield at Fair-rite's other materials you can find material 68: -



Look at how the \$\mu ''s\$ graph is virtually zero in the FM band - it will make a superb balun.

So, in short, go to Fair-rite's web page and review "Inductive Materials" tab of the table presented: -



As you can see, material 68 is recommended for frequencies less than 400 MHz. If you chose the "suppression materials" tab you won't find material 68 but you will find material 43.

As to whether you can get these components is down to who you are prepared to deal with and whether you can get samples at a reasonable cost. In the past I've obtained freebies from Fair-rite and found them to be very amenable but there are other suppliers like Ferroxcube and Siemens who also make similar materials.

Don't expect sensible help from ebay!