When terminal shoulder inflexibility is the limiting factor in getting into a low bar squat position I think the squat bar handles shown in this link could be suggested.
No need to buy another bar with safety squat padding and you are still doing high bar squats
The distance between the handle and the bar can be adjusted to the extent of one's flexibility.
I'm 69 years old and spent over 6 months working on flexibility with Paul Horn stretches daily but could not ever get a stable position but I was determined to do low bar squats. With the handles I can lock the bar in place and my NLP took off. I can get a much narrower grip on the bar than that shown in the link. I would suggest using static climbing rope. I use 8mm which is easy to tie a knot.