I can respect your concerns, but there is so much more to swapping forks than the relatively minor hassle of installing new cables. Those Amazon ones you posted, while potentially the correct length, will likely require extensive mods to use with the rest of your stock components. Plus they look like even if they do fit the stem, they will raise up the handlebar mount position compared to stock, which means - yup longer cables.
The simplest swap would be with another used Puch set or with an EBR set specifically meant to work with Puch loose bearing drum brake wheels. Those options will allow you to use the same headset cups, bearings, wheel axles and hardware, brake hubs, handlebars, etc that are on your existing bike.