Getting hold of those wipes on the High Street has never been easy. I faced the same problem when, back in pre-internet days, I was in charge of first aid in a secondary school. High Street pharmacies never seemed to stock them, meaning that I always had to order them through (expensive) specialist suppliers of first aid equipment. (The 'expensive' bit there was important to me, as the school never had enough money to buy all of the necessary first aid stuff, meaning that I often had to pay for it out of my own pocket!).
When I was having to self-inject at home a couple of years ago, during my chemo treatment, I simply used a bottle of surgical spirit and a bag of cotton wool balls to clean around the injection site beforehand. I now continue to use those two things together to remove the goo left on my skin when I change my HRT patches twice a week.