RE: Any compatible stylus with Inspiron 15 7000 (7558)?
It depends on what you want from the system. This is a touchscreen system - it's not a digitized-screen system, so any stylus will simply serve as a stand-in for your finger. It's not going to add handwriting or drawing to the system -- for that you need something like a Surface Pro 4, Thinkpad Helix or X1 Tablet, or a Yoga Pro -- so far Dell hasn't entered that marketplace, and it's a market that starts near the $1K price point and rises quickly above it -- you're just not going to find a true tablet system under that price, largely due to the cost of a digitizing screen.
If you just need a simple stand-in for your finger touch to keep the screen clean, something like this will work: