MCX and Mini MCX (MMCX) are different. Many Garmin GPS receivers have an MCX connector, and it's slighly bigger than the MMCX.

A Google web search shows a number of companies that sell MMCX and Reverse Polarity MMCX connectors. Generally you'll have to buy them in lots of 25 to 100, and have a special crimper tool (or the dies) to properly attach them to coaxial cable. And of course, you'll have to buy that tiny coax in lots of several feet, most companies require a 50 to 100 foot minimum purchase for stuff like LMR-100 (It's only about 30 cents a foot). Although in the past I have soldered coax to a crimp-style MCX connector with success, I wouldn't even attempt it with the smaller MMCX connector... I've also very carefully crimped MCX connectors with a pair of vice-grips.

For most of us that means that purchasing a pre-made pigtail will be easier and cheaper.

I had custom pigtails made for both my ORiNOCO card and my Linky WAP11 for about $70 including shipping. Had I purchased the bulk materials (and a cheap cripmer) for the JUST the Linksys AP, It would have set me back $98 (not including shipping). Those were the RP-TNC connector, 8 feet of LMR-400UF Coax, and a male N connector. I could buy the RP-TNC and N Connector in singles, but most places wanted a minimum 50 foot order on the Ultra-Flex LMR-400 at 70 cents a foot. Plus a cheap crimper that would work was about $36.

Note that the "recommended" Times Microwave Crimper sells for about $250 PLUS you have to purchase the correct dies at $135 a pop. Then they recommend the coax prep and center conductor deburring tool that are about $85 and $50, respectively. Lessee that adds up to: $520