IF YOU ARE HANDY ...
FIRST, you need to cannibalize the
receiving post from a (
vintage) clamp-on downtube shifter ...
THEN, you will want to fabricate a DIY strap which will replace the original strap ...
Make a template from a manila folder OR whatever material is handy for you to use ...
Figure out where you will be "folding" the strap & (especially) where you will drilling the hole which will receive the post ...
CONSIDER installing an auxiliary steel washer between the strap & the post's base ...
You will ALSO want to epoxy a small "stop" on the frame's downtube which is effectively a
cleat which will keep the DIY strap from slipping down the downtube
!!!!
Depending on your sensibilities, you can use EITHER a 12" piece of brass stock (
¿ 3/8"-to-1/2" wide ?) OR cut-and-fabricate a strap from a large tin can (
!?!) ...
Round the corners & coin-and-debur the edges!!!
Secure the ends by mimicking the standard clamp.
PAINT the DIY strap if you use almost any type of steel ...
DONE!!