The champions were awarded their individual medals after the 0-0 draw at the Etihad last weekend, but players with fewer than five appearances this season did not receive one.
Both Foden and Diaz can secure their Premier League medal with a fifth appearance against Southampton on Sunday, but Guardiola is annoyed that the pair were excluded before.
"I didn't know it, but it looks ridiculous to me," he told reporters.
"If they want my medal I will give them my medal. They are champions, they worked from the first day to the last one – training, in the locker room, more training. They didn't play because of my decisions, but it's the same. Tosin too, from day one in training with us.
"They are champions - it doesn't matter they don't have medals. Maybe it's so expensive to give three, four or five medals for the young guys. They are all the time training with us?"
The club have been handed 40 winner's medals to distribute among the players and staff.