What size rims does your bike have?

You won't find dual sport tyres in the size you need, and anything you do find won't be safe or weight rated.
Maybe take a look at a classic tyre
https://www.cokertire.com/tires/styles/motorcycle-bike.html#tire_rim_diameter=116

The pictures aren't showing anymore but the bloke in this tread https://www.hdforums.com.au/Thread/670217/1 was doing a little riding on dirt roads.

Find yourself a set of street bob wheels.

You'll get much better variety of tyre in the 19/17 combo

And you'll still have your 48 wheels and tyres should you want to switch back.

PS I run Heidenau K60 Scouts on my beemer in 19/17 sizes.

Good find !