Recently, there was a thread looking for a backpack that would fit many European airline personal item size of 40 x 30 x 15cm.
I had one that was close enough if not packed to tight. But thanks to a frozen shoulder, it makes putting a backpack on, with any weight, excrutiatingly painful.
Time to switch to a holdall. I found exactly what I wanted. The Cabin Max Manhattan Holdall.
It's 40 x 30 x 15 cm expandable to 40 x 30 x 20 cm. So it could do double duty as a single Ryanair bag or a personal item with the European non-discount airlines.
There aren't a lot of internal pockets which is what I prefer. It has a water bottle pocket, a laptop pocket, and a luggage pass thru.
The only downside, of course, is that I can't seem to find it for sale anywhere in the US. Since US airlines personal item size is bigger than most European carriers, the bag manufacturers don't think this smaller bag will sell there.
I bought mine via Amazon.co.uk but it was shipped from Cabin Max. (The Cabin Max website shows it as sold out but it arrived within one day to the UK when ordered from Amazon.)