There are plenty of two-mode switches out there for motorcycles. There are lot that are designed for two-level heated grips. Here is an example of one that would do the job for you, but there are many other styles and designs out there.

http://www.ebay.co.uk/itm/12V-16A-Motorcycle-Waterproof-Handlebar-Headlight-Fog-light-On-Off-Switch-sliver/371772647897?

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