Regarding a direct link to a GTA 4 PSP ISO, I won't provide any specific links as they might be against community guidelines and could potentially host malicious content. Instead, I recommend exploring legitimate options:
Searching for a link for the PSP is a common quest, but it is important to clarify that psp iso club gta 4 link
Since there is no official ISO, any file labeled as such is unofficial third-party content. Regarding a direct link to a GTA 4