Recently, I've seen arm rests that have a different mounting option made specifically for the Mirage. Since I changed my seats to the red-stitch LE ones, I thought I'd get a matching red-stitch arm rest with the new mount. Below are the pictures of my install with some other options with the new mount. The arm rest itself can slide for and aft, and so does the actual pad too, great adjusting and comfort potential.
https://www.ebay.com/itm/Dual-Layer-...MAAOSwXNReumnE
https://www.ebay.com/itm/For-Mitsubi...EAAOSwmhlft~fN
https://www.ebay.com/itm/Dual-Layer-...Cclp%3A2334524