Well as I'm new to this I don't know if my experience counts for much (I've used cheap and homemade strops, which were a lot better) as it's been with knives in the past but I find almost any leather works to some extent. I've used plain old 9oz veg tan and saddlery butts in the past, sometimes with homemade paste e.g. linde A and lanolin or neatsfoot oil etc. and found it works well enough. The only reason I've stuck to making my own compounds and leather is because I've had the leather left over and I've found getting information on the grit size of the available compounds is difficult in the UK.