The Blackhawk adapter will work reasonably well and is, IIRC, only $8 or so.
Some single-point slings may have long enough webbing at the attachment end that the webbing of the sling itself can be looped around the narrowest part of the stock without needing to use the web adapter.
If it's going to be fairly permanent, I would suggest just adding a sling loop (or quick attach stud) at a good point on the stock, which again will only set you back $10 or so, and requires only rudimentary skill with a drill and screwdriver.
I will say, though, that I don't think a single-point sling is a good choice for very many users, as I think the "tactical" 2-point slings provide far better control, comfort and convenience for absolutely everything except shoulder transitions, and are quite manageable for shoulder transitions as well.
I would suggest you consider one of the following slings as offering multiple options:
Spec-Ops Gear "patrol sling" which works as a great 2-point or a good 1-point
Spec-Ops Gear "T.H.E. Mamba sling" which works as a great 2-point, a very good 3-point, or a good 1-point (note: only the "T.H.E. Mamba", the regular Mamba sling is only usable as a 3-point)