The attached photo shows a Duo-Art pump motor assembly.  I have just
started this refurbishment, so there's a lot to do both functionally
and cosmetically, but I decided to show the material I use to replace
the original leather cord tensioning strap that rarely survives.

What I have used is a short length of a 1/2" wide fractional horsepower
drive belt.  Should be otherwise self-explanatory.  I don't plan on
replacing this (particular) strap again!

John Grant

 [ http://www.mmdigest.com/Attachments/18/08/13/180813_131452_Duo-Art_Motor_Tensioner.jpg