You can get away with most 'off sounding notes' in ragtime just because of the speed of resolution. Most rags uses a lot of chromatic notes that clashes with the melody or harmony unless you play it fast enough. There are a lot of walking bass lines with chromatic movements and if played slow they can clash with the harmony or vice versa, but if you play it at a normal speed and they resolve fast enough back to a diatonic tone, it gives more like a 'color' to the song instead of an off-sounding feeling.
Other than that, I know that 8notes has a lot of scores, sadly they are more often than not not too accurate. They are probably fine for simple songs like hymns, but not that great for more advanced scores, because they often have mistakes in them.
Especially for ragtime, I would always search for an original score. Because many of them are already in public domain (copyright free, because they were written before 1929), you'll find a lot of copies of the original scores online. Here is for example just the first page of the song you're looking for. If this version is too hard to play for you, you can just simplify them yourself ;)