My first real size one asin not the small kind you can pick up single handed came with replacement o rings. Not sure if the new one I bought after that did or not.
Alibaba has all the seals and related parts for repairing jacks. I used one seal that lasted a day, I’d ordered a few so I think I got my nickels worth
When something comes new with spare repair parts I find that concerning. That doesn't give me a warm and fuzzy feeling.
Someone is sleeping in the R&D lab.
I have gotten replacement o-rings with some tools. The problem is where to put them. I have been collecting tools for 30 years and moved 4 times so stuff gets mixed up and there is a lot of stuff.