From the announcement:
Demand for the Maus has been overwhelming and as such production is underway to provide more as soon as possible. Pre-order yours today to be first in the queue when the new casts arrive over the next few weeks!
Unsurprisingly this is a challenging model to cast so we only have a limited stock available at release. After this initial stock is gone, we will cast your Maus to order especially for you, so there may be an extra wait.