The Japanese electronics and entertainment company has been pushing the successor machine, PlayStation Vita.
Discounts on Vita and downloads are offered to Japanese PSP owners, but are still undecided for those overseas.
More than 76 million PSP machines were sold, as of two years ago, the last time a tally was taken. The PSP went on sale in December 2004.
Machines devoted to games are struggling against the popularity of smartphones and other devices. Sony reported a $1.3 billion loss for last fiscal year and is expecting to stay in the red this year.
Some analysts say the Vita has not sold in significant numbers. Sony does not release the cumulative global unit sales of the Vita and combines it with PSP tallies.
Sony's handheld game machine also faced stiff competition from Japanese rival Nintendo Co.'s 3DS. But Nintendo has also struggled to keep momentum going for its game machines.