These are the ones I use:
http://cognitomoto.com/collections/motogadget/products/m-switch-3-push-button-housing-7-8-black-blackIf you have smaller hands, these are quite nice too:
http://cognitomoto.com/collections/motogadget/products/motogadget-m-switch-mini-push-button-housing-7-8-blackAnd those are "pre-wired" form the buttons.
It's hard to find the stock striped colors, so I use solid versions of the stock colors as much as I can. If you use the m-button, I'd suggest following the MotoG color scheme then. And last knock against the m-button, it's not as a clean to use it with clip-ons. You wiring will leave the bars thru the end then want to turn around the steering neck, and run under the tank to the backbone to connect to the m-button. There, all the wires will cross up and over the backbone to connect, then a single wire from the m-button to the m-unit. Problem is, the m-button is hanging out with all the wires connections.
Or, you put the m-button in the headlight bucket, and the wiring exits handle bars and turns into the bucket, then a single wire back out. (This is a ton less clean). I'm telling you, for simplicity, for clean looks, and ease of connections, ditch the button. Save that money and spend it on something that actually makes your bike run better, faster or jump higher.
There is also a potential electrical interference with the m-button if you are not using resistor spark plug wires. The 650 is a CDI if I'm correct, so this is something to plan for.
The m-switch I linked at the top has another button on the "front" of that housing for the 3rd function. I use it as a my START, then the right lower is my Turn R, right top is my menu (for a MotoG gauge). Left side is front Horn, top is HI/Lo and lower is Turn L. So you can either get a 3 button and a 2, or have the spare function on yours in case you ever swap to an electronic gauge.
You send me a detailed list of which components, and I'll send you a colored diagram back, and I'll do it in stock colors so the next owner of your bike can decipher the wiring from the stock diagram.