Why are you typing anything in a grocery store? Type in the kitchen when you need to add something to the list, but in the store it should be just checking off the items as you put them in the cart. Maybe you have a good reason, but it feels like you are solving the wrong problem. [insert long rant about usability and human-machine interaction]

If you really need a keyboards I agree bluetooth keyboards are chunky. I often use a 60% keyboard with my phone, but it is a lot larger than my fine despite being a small keyboard. There is no getting around the size of hands though, you can't make a good tiny keyboard (even a 40% won't fit in your pocket).