Suehiro Toishi is a Japanese whetstone manufacturer that has experience making a wide variety of whetstones for various applications since the 1960s. Known for their popular Suehiro, Cerax and Gokumyo ranges of whetstone, whatever your application, Suehiro will have a Japanese sharpening stone for you.
In particular, they make specialist whetstones for sharpening sickles, chisels, pruning shears, and of course, kitchen knives. If you're looking for a sickle sharpening stone, you've come to the right place. Suehiro's whetstones are categorized as "artificial whetstones", which sets them apart from the natural Japanese sharpening stones that have become popular recently. Artificial whetstones are less likely to break, and can guarantee a higher purity in the grit, to avoid scratching your blade. Suehiro's stones require less soaking than other brands, as they use very little bonding material in the whetstone manufacturing process.
If you want to keep your tools sharp, rust-free, and in their best condition for as long as possible, invest in a great whetstone.