Vintage Synth Repair

> So, any help is appreciated. At a glance it sure looks like a damaged 
> custom chip, but naturally I'm hoping to get away with just 

Thanks to Timothy's Ebay item (extra neat manual btw, well worth the 
price!) I now got a bit further with this case and it indeed seems like 
the custom VCF chip (iC27, IG00156) on osc2 is shot :(

So, would anyone have any suggestions as to where to source these chips? 
Vintage Planet seems to be out of stock at least. Does anyone know has 
there been any attempts at cloning this chip or are there datasheets for 
this chip available somewhere?

Regards,
.Arto.