Yes, if you cannot find exactly the part you need (wrong size, wrong coating, etc) you have a few options.
1) Submit an RFQ request here : https://shop.specialtybolt.com/sourcing/rfq OR
2) https://shop.specialtybolt.com/quoterequest/ Click the button "+Add an Item" then flag the "Non-Stock Item" and add the part information in the description field. Feel free to add McMaster-Carr or other supplier part # if necessary.
3) Find a part that meets some of your requirements. Select "Add to Quote" under the "Add to Cart". Add the quantity you need and in the Item Note field define what you want different. Example : This part but stainless steel and 100mm long. On receipt of the request we will assume you want the part as built except for the material and length.