The 28mm ones will work fine. The ID of SF hilts are listed at 1", but the body sections are a bit wider on the inside. Those who were looking into the 20mm ones were planning on putting them inside the pommel instead of the body to save space.
Here's the bass-style speaker the ASP kits use and a TCSS 28mm bass speaker, and they have the same diameter, though the TCSS is a bit deeper. For their regular Champion and Hero installs SF appears to use the same size premium-style speakers.
Interestingly enough, when I was putting the two of them up to each other to compare their size. the two speakers attracted each other.
TCSS (The Custom Saber Shop) carries pretty much everything a saber builder needs,
including 12mm AV momentary switches. They only carry lit ones, which have separate legs for the switch mechanism and the LED. If you do want to have the switch lit, you'll need a resistor for that.
I'm I correct in assuming you'll be wanting a red LED? If you weren't aware, the wavelength of light the red Cree LED dies SF uses gives off (which is in the same range as other red Cree and Rebel LEDs used in the lightsaber hobby) combined with the frosted/trans-white blade, gives off a slight orange hue. It's still definitely red when you look at it, but not exactly the red seen in the films (which is actually a bit difficult to pull of IRL). There is an older die model that has a red (called photo red) that gives off a much deeper red and looks really great in lower light, but it isn't as bright and gets washed out a bit in brighter light (I have a photo red Tri-Cree I've wired up, and can attest to this), like one would encounter at a convention.
Not trying to deter you, but just inform you so you aren't surprised. SF red will still look really great and will be much brighter even under daylight.