If you bought the bike new, see what the shop has for helmets and what they recommend. If it's a recent new bike purchase, see if they will grant you some kind of accessories discount if one was not offered in the first place. The same place which sold you a Trek should also sell the Trek house brand of helments, Bontrager. The Solstice is their cheapest helmet, one size fits most; next level up is the Quantum, which comes in different sizes for better fit and style. These are more typical bike style helmets, with many vents and some angular styling.

Most shops also sell other helmet brands and even though I work in primarily a Trek shop, Bontrager no longer markets a nice skate-style/"Urban" helmet with fewer vents and a rounded shape. I used to wear a Giro Section, still in production, now wear a Surface, which looks like it has been discontinued, or replaced by their Sutton/Reverb soft brim design.

When I eventually need to replace mine, I'll also be looking into POC (Receptor and Crane models) and Bern helmets, with Bern probably getting the nod due to visors. I like visors...

You should be able to hook up lights to any of these. I gave up on a helmet mounted headlight, but my Giro Surface has a zip tie through two back holes to accommodate a blinky red taillight.