I don't think leather belts can be used,not hygienic and not secure enough.Plastic seems a better choice,but I'm not sure there is similar plastic chastity belt for women,than there is plastic chastity cage for men.Steel is the more safe and more secure one(but can too be used as a sex toy in a couple).
About putting men in chastity cages;I agree it could be more fair,but,as I said elsewhere here,there is much more pain implied for them,and may cause some damages...