What's the best way to show a guy I like him in an abnormal social setting for flirting?

I have a crush on/have been flirting with a guy who works at a grocery store and it seems evident that he's aware of my crush (maybe he isn't, but it seems like it) and he is flirtatious back. Of course when I interact with him, depending on how many things I am buying, our conversation will last 30 seconds-5 minutes. There have been a few times where he has been so caught up in talking to me that when the conversation lulls he realizes he hasn't bagged my things and will quickly start. Also, two days ago I bought a pumpkin and while we were talking he accidentally put in that the item was pumpkin pie and had to change it. He has shown basically every sign of interest aside from touch, because as a cashier it's really weird to touch a customer, and vice versa. I am shy and I blush easily and get embarrassed so I sometimes briefly don't look at him while we talk, but generally I do really well with making eye contact and smiling. I also noticed he will watch me leave the store/walk past his register and if I look at him he will smile and tell me to have a good night. I have been wanting to compliment his recent haircut but the first night I noticed it I forgot/was nervous, then the second night there was a girl waiting to take his place and I felt like it might be weird with her there especially since she isn't a customer and was listening to us. What would be the best way to show him I'm interested especially when conversation is sometimes on a time constraint and he's working? I mostly don't want to isolate him or make him feel like I'm only being friendly and that I'm not interested. Since this isn't a setting like a bar or class I can't show him through: touch, getting close, or bluntly asking personal questions or even to hang out.
What's the best way to show a guy I like him in an abnormal social setting for flirting?
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