Instead of different shockmounts, you might also consider sticking with the A20's but always keeping a 5/8"-male > 3/8"-female adapter inside the shockmount and a 5/8"-female > 3/8" male adapter on your mounting bar. That way, you're only ever screwing into and out of the 3/8"-female portion of the shockmount setup and never wearing the plastic 5/8" threads.
Or (and maybe in addition to the above), if you have an active setup and only use a single shockmount, you could quasi-permanently affix the A20 to a
Bogen Rapid Adapter. Want to take your shockmount / active set up on and off your mics stand? Just loosen the Rapid Adapter and pull it off - again, no wear on the A20 threads.