I received this reply from Steele Rubber may be of interest:

"Thank you for your inquiry. We do not offer this lock pillar filler for the 1961 Valiant as we haven't had enough request for this part nor had a decent original part to research the cost involved making the mold for the part and production cost of manufacturing it. And a big determining factor is if we could sell enough to justify the cost involved. If yourself or someone you may know has an original part to offer to our research department, you may contact us at 1-800-544-8665 Monday to Friday 8am to 5pm Eastern Standard Time.
We appreciate your business and hope you have a wonderful week.
Have a wonderful day.
Steele Rubber Products
Denver, NC"

I don't have any door lock pillar seals, maybe someone else has that could be used by Steele Rubber.