The DL-1A dummy load can handle a full 20 watts for 30 seconds maximum and 10W 1 minute ON, 1 minute OFF. Its SWR is less than 1.3:1 through 200 MHz. It includes an integral RF detector for use with a voltmeter, allowing you to calculate transmit power.
The DL-1A Dummy Load it is discontinued.
However, you can freely build it yourself
I share the file to make the PCB (Sprint Layout 6.0). Download.
You will need to have the Sprint Layout viewer. Download.
DL-1A kit assembly manual (schematics, parts list etc). Download.