Where can I get Custom Mechs?

Custom mechs of limited characters can be collected by using Bits, which you’ll earn by pulling on the limited pilot’s Special Recruitment banner. This is the only way to get these custom mech parts and may require a lot of bits (and a lot of draws). If you can’t get the whole set, you can settle with the weapon at least.

Other custom mechs can be obtained from limited events. For example, Aya Kujyou’s The Ronin mech can be farmed for free during the Shadow of Corbero event. You can get the Rank 60 version of it by clearing all 40 loot boxes. It may take several days but at least it’s free. (Sadly, Aya’s skills doesn’t have CMSA bonus effects)

Finally, some custom mechs are only available by purchasing them outright using real money.