From their website:
You may have noticed a few items such as the ARC Fleet walkers have gone out of stock in the store whilst we make new moulds and await new metal stocks, we had previously taken these items off sale but several of you have requested to purchase these items before the price rise on the 18th October.
As such these items are once again in the online store for order and we will dispatch these items as soon as stock becomes available.
A special note should be made regarding buildings AFBD2, AFBD3, AFBD15, AFBD16, which will remain unavailable for the time being. The reason for this is two fold. Firstly the moulds have failed and secondly we are not happy with the design of the masters for casting. As such they are being reworked to produce a better end product with a slightly different design. We hope to have these changes completed by mid November.
We apologise for any inconvenience this may have caused.