I'd experiment with cornflour (cornstarch), tapioca flour, potato flour (although it has a tendency to make things 'spongy'), or even plain wheat flour (if wheat intolerance isn't an issue).
I'm 'sailing by the seat of my pants' here as I don't generally use it, however, my initial thoughts would be to use it at less than 2% of the meat weight.
Looking through some Dutch Rookworst commercial manufacturing recipes, who are a bit similar to Frankfurters, they suggest that you can use up to 30 grams of Potato or corn flour per 1 kilo of meat. Other flours are also recommended same weight per 1 kilo of meat. Cheers, Jan.