Cat leash/harness

Hi I have 2 kittens I got as b-day and sobriety gift for my self. I come from a semi active family and I visit my parents who lives spending. Times out doors. Hiking riding on a side by side etc.

I am looking for a brand that sells cat harnesses for my kittens. They are 10 weeks old but the female is smaller than the male (brother and sister). I am a first time cat owner. Thank you all for any help you can provide!