Petite Jeans inseam 26" is equal to 66 cm. Finding them is not an easy task, we should admit. What makes it even harder is the various interpretation of the size "Petite". Some stores categorize "Petites" by height (5"3' or 5"4' or 5"5' and under), while some, no matter your height, define tiny body frames as "Petites".
All what I am trying to say is that not all Petite Jeans you find online can be jeans with short inseam, if that's what you are looking for.
Appleseed's petite short length pants are of inseam size 26". As well as denim jeans you can also find knit, twill, corduroy pants all in your size.
Blair's petite stretch classic style jeans come in short inseams 26" and 27" as well as other regular inseam lengths. If you dig deep down sometimes you can also find jeans with inside leg 25". You can find comfy petite pull-on denim pants.
Gap Denim features some very classy jeans for petite women and girls. You can get them for under $50 in petite inseams 25", 26", 27", 28" 29" and 30". They also have Regular and Tall jeans. International delivery is possible.
Lands' End carries a good collection of petite full length jeans in popular inseam size 26". This link will take you straight to their jeans section with size 2 jeans in leg length 26". You can choose other sizes from the left-hand column dropdown menu. For around $50 they feature mid rise and high rise jeans of various leg styles such as straight, bootcut, wide leg, skinny and more. They keep US sizes from 2 to 18.
Marks and Spencer carries short inside leg length jeans for petite women. You can find them in legth 26" and 29". For under £35 you can choose from slim leg, bootcut denim jeans as well as straigt leg jeans. International worldwide delivery service is available.
Marisota offers jeans in sizes from 8 to 28 with petite inseams starting from 25" and above. You can choose between the UK, Ireland and US sites.
Zappos petite jeans section
has some jeans in inseam 26". It's easy to find them on their website,
as you can choose by inseam length. The link above shows the search results for over a hundred jeans with inseam sizes 26" and 26" 1/2'. So you have plenty to choose from. Zappos carries jeans from many well-known brands such as 7 for all Mankind, Hudson, Ivanka Trum, Paige and many more.