The starter button's easy, you just need a normally off push-button that can handle a bit of current, nothing major. You could even use a spring loaded toggle or rocker switch if you wanted, but why re-invent the wheel?
When you say on off switch, do you mean the engine kill switch or the ignition switch? If it's the ignition switch that's less simple as you'll need a "triple pole single throw" (3PST) switch just to do the ignition, and that'll lose the "parking lights" position. If it's the kill switch (which is what I suspect you mean) that's pretty easy, a simple on/off toggle switch will work fine, just ask for a "single pole, single throw switch" (SPST)... toggle, rocker, or whatever other style floats your boat. I'd use a toggle switch so you can easily feel it with gloved hands in case of an emergency, but if you decide on a rocker switch (like the original one) use the biggest one you can find. I'd put your switch box on the right side of the bike rather than the left, so if you do go over you can still reach either the ignition switch or the kill switch, depending on which side the bike's down on.
If you'll be riding at night you might want to include a high beam switch too, since you're already going to be extending wires and mounting a switch box... that's a simple "single pole dual throw" (SPDT) switch. They're hard to find so you'll probably end up using a "dual pole dual throw" (DPDT) one and just ignoring one of the poles. If you did this I'd use a toggle switch for the kill and a rocker switch for the lights, so you can feel the difference. You don't wanna go for high beam and kill the bike instead.
FYI, a "pole" in this respect is like an individual switch and a "throw" is how many "on" positions it has. A simple switch that connects two wires has a single "on" position and an "off". It will have two connectors. You can get a switch with two "on" positions - it will have 3 connectors, one common connector and two "on" connectors. These can also have a "centre off" (on/off/on) or just two "on" positions (on/on). A dual pole switch is like taking a second switch of the same sort and putting it beside the first switch, so you can turn on two separate things at the same time (for example, turning on an ignition coil and an electric fuel pump, through two separate fused supplies). So a DPDT switch will have 6 connectors, 2 central "commons" and a pair of "on" connectors for each "common". It may or may not also have a central "off" position. Confused yet? Here, I'll draw you a picture.
