Bob - hubby and I each use a RS convertible backpack, XL Laurel Burch tote, and Travelon x-small crossbody purses for daily use.
The backpacks are our main bags. We pack nothing but clothes and such in those bags.
The zippered tote is our personal bag. We just use them during transit, not as day bags while on the trip, but we have used them to pack two days of clothing for overnights when we didn't want to carry everything with us. I used to carry one of the totes as my daily purse, so for me it would be easy to carry something like this as a daybag. They are quite colorful bags so you might prefer something more subdued, but by listing the brand name you can look at it and get an idea of it's features and size. I especially like that the insides of my bags are plastic coated to keep stuff dry or to easily wipe out if something spills. All of our important stuff (meds, tablets, chargers, etc.) go inside the totes. Make sure that whatever you buy for your personal item is zippered or can be secured against easy pick pocketing. You don't want someone to be able to casually stick his hand down in there and get some goodies. We also stuff our purses in the totes during boarding as they only want you coming on with two items. We were using a large pacsafe crossbody as one of the personal bags, but both of us quickly became irritated as the bag was slick and bad about sliding up the side of our necks during transport when the bag had to be carried. I prefer the shoulder bag and am very careful to keep it looped over my shoulder during short jaunts on trains where pickpockets are likely to be.
We love our Travelon x-small purses. More secure with the locking zippers and ours are both very lightweight. I use the signature pouch and hubby uses the classic small tour bag which is plainer and "more manly" lol. Keys, smokes, transit cards, tissues, sunglasses, phones, etc. easily fit in the crossbody purses so we have found that is all we need for jaunts around the cities or out in the boonies day tours.
We also took the RS Civita backpack on a month long trip to use as a daybag and it performed wonderfully for hiking in Switzerland.