This feature already exist with some domain registration for small fee, check with your domain registrar for it or search google for domain with dropcatch script.
My domain reg do not provide this service and i need this for different extension
In that case you could google for domain name registrar that has that features and transfer your domain names there better still you could check freelance websites for a coder.
Freelance people ask for thousand of dollars and this script required very basic coding unfortunately i'm not good at coding
and no such script is available in market