It's in Debian (possibly upstream only), but you can download the latest version from their website and install it manually.
The MX 15/ MEPIS repositories
: Backports galore! If we don't have something, just ask and we'll try--we like challenges. New packages: Variety 0.6.2, Pale Moon 26.4.1, Liquorix kernel 4.7-4, SMPlayer 16.9.0, Corebird 1.0, Caffeine-ng, Mesa 12.0.2