I have a handbag for work, it's quite boring, £2.50 from a charity shop, so I just keep work stuff in there. Personally, I prefer backpacks!
I have a big, fake fur, luxurious, handmade black/white cat backpack from robopets.co.uk. She cost me £80.99 + P&P but is sooo gorgeous! I called her Sophie. There's a special comb and a little neck thing I bought for her, too!
I always keep my house and car keys in my jacket pocket, but everything else is in the backpack.
I carry a little magnifying glass, circular in a black plastic case that's attached to the magnifier, a pack of tissues, a small notebook/pen, I know you all might think I'm loopy, but I'm obsessed with rodents so I have a little fake fur toy mouse where you pull the tail and it whizzes along the floor, from Pets at Home! Cost me £3.00, but that's in my bag too! I've had tons of real pet rodents over the years!
Mobile, purse, small torch, small circular tin of lip balm and a small bottle of hand gel, paperback book, as I've forever got my hooter in one - also a book in my work's handbag -, driver's licence and passport, as I won't leave anything with my ID on it at home.
And anything else, like small grocery items such as a can of Coke or whatever I can shove in my jacket pockets!