QRP-labs.com offer a range of cost effective electronics kits for radio hams. I chose to order and build their 20W Dummy Load kit.
The kit is simple to build, consisting of x20 1KΩ 1W resistors sandwiched between two PCBs with a BNC connector. There is also a diode/capacitor circuit for detecting the peak voltage, if required.
The completed kit is really compact, measuring only 43 x 36 x 15mm approx. (excluding BNC connector). There is also a beauty in the simplicity of this design, maybe a benefit of the QRP ethos here given only air cooling is required given the low power level design.
This Dummy Load Kit is available from QRP-labs.com for $8.50 plus a small P&P charge. It arrived quickly for me, all the way from Japan.
Please see my build photos attached.