I have three different keys and Westlakes Hardware (BoCoMo) had blanks for all three.
If your Dealer had no blanks, go to another dealer, sounds strange he could not get a key for you..... Even if it was 'blanks' and you had to take those to a key shop to get them cut. Have you tried any key shops?
2013 Forest River Salem Hemisphere SBT312QBUD
2001 CrewCab F-250 7.3 PowerStroke Diesel
SuperChip, BTS transmission, 6.0 Trans Cooler