Since you're using SAS/Graph (gmap, gslide, greplay), you will not be able to easily use ODS Graphics (sgplot) with it.
One solution I've used to get a second legend on a separate page in SAS/Graph is to suppress the legend in the real graph (nolegend), and then use 'annotate' on a blank gslide to fabricate my own custom legend on a separate page. Here's an example - the outtput, and then the code:
http://robslink.com/SAS/democd16/topper.htm
http://robslink.com/SAS/democd16/topper.sas
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