Originally Posted by
noobinsf
Is it a friction shifter? If so, is that plate with the numbers and “3 speed” a separate part? Maybe you could swap out that plate with a Sunrace thumb shifter, like the one linked below and have a new shifter with the old look. I have no idea if the dimensions are same, but for $7, it may be worth a shot. At worst, you have a new Sunrace shifter that works.
https://www.ebay.com/itm/New-Sunrace...-/362631435140
The OP's shifter is indexed, each click moves the cable a certain distance. While a friction shifter will work in theory, it will be damned hard to locate the "sweet spot" for the gear change.