It seems that Ricoh Japan has discontinued production of the HD PENTAX-DA 21mm F3.2AL Limited silver lens (buy here). The wide-angle HD PENTAX-DA 21mm F3.2AL Limited was released in 2013, as the replacement for 2006’s smc PENTAX-DA 21mm F3.2AL Limited. It was released as a compact wide prime for walkabout shooting with a small, lightweight APS-C camera setup.
At the moment, it seems that only the silver version of the lens has been discontinued. The Ricoh Japan online store lists it as “Completion of production” with limited (“only a few”) stock still available. Outside of Japan, stocks are still available at some online retailers.