The knox right hand trail and right leg trail out of stock that what it says when i try to buy it but everything else is good is there a fix?

Items go out of stock when lots of people purchase them, meaning there is no more available until the store is restocked. If I remember correctly, the store is restocked at the start of every month at GMT +1.

However, you can always try the market if the item you're trying to purchase is out of stock.

Albus pretty much says it all.
The market ususally has the item you are looking for, and usually at a cheaper price.