Here’s my take on this, and it’s a tough situation to be in.
Your most direct route is going through Snapchat itself. I’d suggest immediately contacting their support team and explaining what happened. Sometimes they have a short grace period where data isn’t permanently deleted from their servers. Also, try using Snapchat’s “My Data” feature to request a download of your information; there’s a small chance the deleted files might still be archived there.
On the other hand, you mentioned tools. While many third-party recovery apps exist, they can be a mixed bag. Their main drawback is that they typically scan for locally stored files on your iPhone. Since Snapchat Memories are saved to the cloud, these tools have a very low success rate for this specific issue. I would proceed with caution if you decide to try one.