The Ratchet & Clank PS2 trilogy (1, Going Commando, Up Your Arsenal) plus Deadlocked and Size Matters (PSP/PS2) are sought-after classics. Here's where to find them.
Some titles are available as PS2 Classics on PS3, PS4, and PS5 via the PlayStation Store. Availability varies by region.
For playing: Digital on PS4/PS5 is easiest. For collecting: Hunt CIB copies on eBay/Mercari from reputable sellers.