Boss HM-3 Hyper Metal

Another one for the metal heads.  The 2SK184 JFETs can still be obtained from some sellers on eBay, but it's just a buffer at the end of the day so you can use others with the same pinout like 2SK117, 2SK170, 2SK30, BF244A etc.  The transistors used in the gyrators though don't seem to be readily available and I couldn't even find a specific datasheet so I've used a CBE pinout so you can use a modern NPN transistor like the 2N3904 or 2N5088 etc.

There was a DIP8 version of the M5218L made by Mitsubishi, but they may be hard to source now, so any common dual opamp can be used in there such as JRC4558, TL072, NE5532, LM358 etc.

Info about the original:

Despite its compact size, this effect can put out a richand truly powerful distortion sound which can sustain for very long durations.

Two specially designed Color Mix controls provide for wide ranging tone control.

Whether for solos or for backing, it makes possible a well balanced new age metal sound.