While your question is not a great fit for a Q&A website as bags come and go, there’s something to be addressed here:
Ryanair restrictions — this is a common mistake, don’t fret — are not 40 x 25 x 20.
They are 42 x 30 x 20. You can find this information at https://corporate.ryanair.com/news/new-bag-policy-from-november-will-cut-check-bag-fees-reduce-boarding-delays/ unlike the advertised limits these have no mercy at all. That’s why Ryanair communicates smaller dimensions — people will always go over it and this avoids a lot of conflict. But if you want to make an informed choice, that’s the sizer.
A number of really great backpacks fit those dimensions, I posted a few to https://www.dpreview.com/forums/post/64333074
There will be a vlog about bags this size at https://smallba.gs/ stay tuned.