Hi Chip
I was about to reply when that manufacturers usually replace parts free of charge, when I thought to check
Revell-Monogram's website; they'll charge $3 postage.
Not much to pay, but I have to say I object in principle to paying extra for what should have been supplied correctly in the first place. Of course it's a different matter if you've damaged the parts yourself - then it's only fair to have to pay towards replacements.
You could try going back to the place you purchased the kit (if you've kept the receipt or have other proof of purchase) - they may take a different view to R-M and replace the parts for nothing.
All the best
Rowan