If you want to build it yourself, here is the schematic I copied from my notebook. The only difference between this and the prototype is the op-amp. The prototype uses four single op-amps while I plan to use one quad op-amp in the finished product. This change saves money and board space.
Amiga RGB -> YPrPb Adapter Parts List
IC1 - LMH6722 Quad Wideband Op-Amp
C1 - 1uF 35V Radial Capacitor Tantalum
C2 - 1uF 35V Radial Capacitor Tantalum
C3 - 0.0047uF 50V Ceramic Capacitor
C4 - 0.0047uF 50V Ceramic Capacitor
R1 - 6.8kohm 1% Resistor
R2 - 6.8kohm 1% Resistor
R3 - 1.3kohm 1% Resistor
R4 - 12kohm 1% Resistor
R5 - 8.2kohm 1% Resistor
R6 - 3.9kohm 1% Resistor
R7 - 1.8kohm 1% Resistor
R8 - 5.6kohm 1% Resistor
R9 - 5.6kohm 1% Resistor
R10 - 75ohm 1% Resistor
R11 - 75ohm 1% Resistor
R12 - 75ohm 1% Resistor
R13 - 1.0kohm 1% Resistor
R14 - 3.0kohm 1% Resistor
R15 - 3.0kohm 1% Resistor
R16 - 3.0kohm 1% Resistor
R17 - 75ohm 1% Resistor
R18 - 360ohm 1% Resistor
R19 - 360ohm 1% Resistor
R20 - 360ohm 1% Resistor
R21 - 360ohm 1% Resistor
R22 - 68ohm 1% Resistor
R23 - 39ohm 1% Resistor
R24 - 220ohm 1% Resistor
R25 - 39ohm 1% Resistor
R26 - 130ohm 1% Resistor
R27 - 75ohm 1% Resistor
R28 - 100ohm 1% Resistor
R29 - 680ohm 1% Resistor
You can substitute the LMH6722 with another op-amp suitable for video (i.e. wide bandwidth). Something like the LF347 will not do because it's bandwidth is too narrow.