have you ever tried SFM? you can apparently download octoling/inkling models + hairstyles,clothes,accecories hats etc and use SFM to dress change the body colors and pose your inkling/octoling, i keep procastrinating because it's really hard to learn how this program works but for people like me who can't draw this is the only option i have for my splatoon characters.
Squidboards
Coolkid
Cephalobro
I haven't tried it yet, but I will try it once I get a new laptop because I heard that SFM requires a lot of memory. But I have seen a bit of it and it looks like you can make your own hairstyle or at least change some of the available ones around. The only problem is that I don't know where to find it.
Coolkid
Do you have a steam account? if not you can make one for free! and the great thing about SFM and all the splatoon and other stuff you can download for it is that it's all 100% free! so you don't have to pay for it.