I dunno why they couldnt help.... I just went back to the website to figure it out and I am pretty sure you want one of these (depending on wire size)
https://www.grainger.com/product/SHR...k-Tubing-3KH57
https://www.grainger.com/product/SHR...k-Tubing-3KH56
website says both are in stock at the 49th st shop.