Can I add patchcables and knobs to an already placed order?

I place an order for a few extra modules, and this order is not processed yet, which is not a problem at all for I have enough new modules to discover and play with. However, I noticed that I'm missing some patch cables and black knobs and I was thus wondering; is there a way to order these and add them to the previous order so they will be shipped together? If so how do I proceed? I do not mean to jump queue whatsoever, the only reason I'm asking is because we're talking patchcables, not modules which I would expect don't create a lot of handling/assembly overhead compared to modules.