Velleman Tremor Tremolo K8110
A complete kit including everything needed to make the pedal shown here: Drilled case with decal, PC board and all parts including high-quality Neutrik jacks. This is a sophisticated optical trem similar to the Tremulus Lune or Tremulous Bear. It offers choice of square wave or triangle wave modulation and has LEDs for power and LFO. You roll your own photocoupler using the phototransistor included in the kit, though the circuit and the board will clearly accommodate any LDR that you want to try. True-bypass in/out switching.
Here are the schematic
and the Plain English build instructions.