Hi 
I would like to recommend my own plugin for this use case, Web-API which offers tons of endpoints to interact with your server.
It doesn’t have a shop itself, so you would still have to make a website for your actual shop, but you can use Web-API to communicate with your minecraft server.
You can find a list of all the routes/methods supported here
There also used to be Web Control, but it hasn’t been updated in a long time