When I bought my new Canon, I spent an extra $15 on the Holga toy lens for SLR. The film I developed from my Diana look no different from the digital version. On the plus side, I don't have to wait a month to get them developed and instantly know if they didn't turn out. Same vignette and light leaks but in RAW.
If the photos turn out too dark, just change your ISO or shutter speed.
Here are some photos I took one early morning.