smaller than stock 200s rear sproket

[1984 honda 200s]

G'day lads, just wondering if a 200x rear sproket would fit on a 84 200s, i was wanting to change it to a smaller one like a 36 tooth or something instead of stock 43, i already changed the front from a 11 to a 13 and i like the difference. The local dealership could only sell me a 40 tooth for the S model so he asked me if a 200x rear sproket would bolt on since thay go smaller than 40teeth. Hope someone could help.