I'm looking at OEM transmitters on eBay and mitsubishipartswarehouse.com. 2014's seem to be unique. I see two different part numbers based on when the car was manufactured...
Geez...the list price for one fob may be as high as $400!
I would consider calling a couple of good locksmiths in your area. Back in 2016, I was in a locksmith's shop getting a key cut. I asked about programming a third proximity key fob for my Mirage. He said his software wasn't up-to-date enough to cover that year yet. He told me to check back in a few months. He said if I brought him a fob, he would program it for $50. My Mitsubishi dealer's minimum charge for anything is $110.
I'm not sure how it works, but a used Mitsubishi fob can be "unlocked" so it can be programmed to another car. THIS guy on eBay is even selling the service?!? I've also seen used "ready-to-program" fobs on eBay.
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View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)