Cash Register for iPad? Building a POS.


I'm building a POS/ERP system for a restaurant and will be developing an app.
It's going to be an iPad based POS with cash register, card reader, printer, kitchen display etc. everything that's required in a restaurant.
Can you suggest where can I get all the supplies?
If anyone can suggest specific devices etc. it would be great help. Also, please share the link.

Thank you.