Ответ:

Excuse me. Do you have this shirt large?

Hold on. I'll check... Yes, here you are.

Oh, blue. Do you have it in green?

Large in green? No. Here's a medium. Is that OK?

Oh, no! That's too big for me.

Ah, here's a large in purple!

Great. How much is it?

...

Oh... That's too much, sorry. Thanks anyway.