The old Armorcast Atlas kits are very rare since they are no longer on sale you find some on eBay time to time. I have a spare kit I may consider parting with (contact me on the email address below).
And here's some of the keyed joint inspired by Armorcast design I've been working on which can be retrofitted to models as (if they can accommodate it). It'll allow the arms/legs to be removed/replaced and add pose-ability.
Stay tuned as my next mech is almost ready to be unveiled to the world! As always you can contact me on the address below;