Been seeking out something that works really well for this as well.
Currently I use a heavy canvas messenger bag similar to the one I'm linking below, but I'm sure there's better options out there so curious what others use as a strictly/mostly PC as well.
https://www.amazon.com/dp/B001I15G4K/ref=cm_sw_r_cp_apa_i_OBr0DbRSRQJV8
I used a surplus military messenger bag very similar to the one I'm linking here. I used it everyday for work for just over 8 years. I also used it for travel and when I went back to grad school it took on extra weight daily.
It's currently sun bleached and only showing very minimal fraying. The only reason I stopped carrying it was because I bought a sling pack for a trip and started using it for my laptop.
The messenger bag is still awesome though. It was pretty cheap, has a classic look, and is very durable.
Original Heavyweight Classic Messenger Bag Olive Green https://www.amazon.com/dp/B001I15G4K/ref=cm_sw_r_awd_ANBzvb0T5GSM7
It's not exactly as small as a purse, but I love the thing. Because it's not stiff like a briefcase/leather bag, it kind of "molds" to however much you're carrying. It is extremely comfortable, durable, and unobtrusive. It's inexpensive, too.
I've had mine for about 2 years and have used it hard every day, and only recently has the polyester liner started to rip.
messenger bags are pretty useful. I have a military green canvas bag and I don't think anyone thinks those things about me. Well, at least not because of the bag.
I went with an army surplus green canvas messenger bag. $30 on Amazon.
Edit: link: Original Heavyweight Classic Messenger Bag Olive Green https://www.amazon.com/dp/B001I15G4K/ref=cm_sw_r_awd_1B4wvb0SR8NC7
Can't go wrong with the Jack Bauer bag. There are a few different colors. http://www.amazon.com/Original-Heavyweight-Classic-Messenger-Olive/dp/B001I15G4K/ref=pd_sbs_sg_6?ie=UTF8&refRID=1APSRTMK0MYTGD51RRVZ#customerReviews