After much searching I finally found a way to attach a sling to my underlever springer it would probly work on others of similar size lever.
https://www.midwayusa.com/product/110946/grovtec-barrel-band-set-2-piece-measure-to-fit-tube-diameter-rear-screw-swivel-stud-1-locking-swivels-steel-black?utm_medium=email&utm_source=service&utm_campaign=products-you-might-like&utm_content=product-image-link
https://www.midwayusa.com/product/110946/grovtec-barrel-band-set-2-piece-measure-to-fit-tube-diameter-rear-screw-swivel-stud-1-locking-swivels-steel-black?utm_medium=email&utm_source=service&utm_campaign=products-you-might-like&utm_content=product-image-link