There is really no current substitute, and scoring one on the open market is likely to set you back $50 or more. If you are up to it, perhaps another BBD could be rigged to sub for it with a daughterboard, but that's pretty much it. The only other possibility is to keep an eye open for less desirable BBD-based effects from the same time period. For example, I have one of the plastic-box Commande series Flangers from MXR. It uses an 8-pin 512D, as does the Chorus from the same series ( http://filters.muziq.be/model/mxr/commande/stereochorus http://filters.muziq.be/model/mxr/co.../stereoflanger ). Because these are in plastic boxes and have less functionality, as well as less "cachet" than the earlier cast aluminum-box units, you may be able to score one on e-bay for less than the price of the chip (although maybe not: Vintage 1982-83 MXR Commande Series Stereo Flanger - eBay (item 330323113580 end time Jun-16-09 14:21:29 PDT) ). The chips are socketed so removal is non-destructive.