If he is at a job and you are not at same location but are planning to be there at some point, nothing wrong with him asking you if you can bring something if you will be having the opportunity to pick it up before you go or while on the way there. Hopefully he knows how to find other things to do until that item is needed. Kind of assuming he is working on some new construction, remodel, etc where there is plenty of things to be done. If he is on a service call or some other more specific install, not having an item could possibly be holding up progress period, and if he calls you and you can be or are on the way fine, otherwise he or the apprentice possibly needs to run after that item if it is something holding up further productivity.
