Currently I am offering two types of strops - a fixed strop, that is a felt is glued to the wood base, and a felt pad with a magnetic backing - to be used with DMT plates in 11.5x2.75 and 8x3".
I tailor products to knives I make and I find that felt and honing spray do miracles to 52100 and other steels I am using, so this is a product you will always find in my product line.
I can offer leather strops if there is a demand for these. I would probably start with getting a splitter to guarantee the uniform thickness of the leather. A good manual splitter costs in mid to high hundreds and a good electric starts at about $1500. If I get 20-30 orders for leather strops, I would bite a bullet and get a splitter. Otherwise, it's just an impractical use of resources (limited, unfortunately, as I still have a huge "to get" equipment list).
Same applies to balsa wood. Is there a demand for it? How much demand?