You just lay the ground rules, they 1) pay you the cash up front, 2)or order it online themselves and have it delievered to your address abroad (this no one wants to do anymore because of the tax, but it's still cheaper than here), 3) Tell them they have to source the item themselves -- ie you say this is the address of where we are staying, you find it in stock at a Best Buy / Target / what have you nearby and we will get it, 4) Tell everyone you are only going for one week and will only be taking 1 day to shop, if they haven't figured out all the money / location of item / if item is in stock etc before that date, too effing bad.
We used to be super generous too, then I got sick of my husband spending 3 days or more of a 10 day trip running around researching which camera to get his dad / brother / guy from the office. I mean they would just say, I want a camera, you figure out which one is best and get me that one, I'll pay you later. We (namely, I) got sick of the requests -- people from his work who have never talked to him before would come to his office and ask if he would buy them a pair of shoes for their wife's sister's niece's cousin etc etc. So now it is close family only (with a couple of exceptions), cash up front cold hard USD, and they have to send us an email with the link to the exact item they want showing it in stock somewhere within the vecinity of where we are staying. I'm not doing and research and I'm not driving 100miles to get anything. We have a couple of friends who we have much more flexible arrangements with or that we even call ahead to say we're goiing because they do the same for us.
EDIT: Oh and any extra baggage costs get passed on to the purchaser -- and the fact is now that most of the time I'm travelling alone with my son, no one dares ask anymore anyway.
