Might want to go ask/search at the zaurususergroup.com or externe.net forums. I think I saw someone mention the 5500 stylus will fit the c7x0 line (and thus probably the 860). He might have meant "fit, but with some sticking out" or something though so try 1 first. ^^ Since the 5500 is sold more widely those would probably be easier to find.
Btw, daaaayum, wish I worked at a company with hundreds of expensive Japanese PDAs. ;p