I just put one of these on my GS500. It is looks good on the naked version, is DOT legal, and has the same bulb socket (h4) as my 2006 GS500F
Emgo Honda Style 6 1/4in. Headlight Assembly - Black 66-64313 https://www.amazon.com/dp/B0068C0QJY/ref=cm_sw_r_apan_i_XB1VVWBXA8PYFWRNXGDX
You'll also need 2x bolts for it. 10mmx1.25mm 25mm long. You can get them at most hardware stores.
If your bike doesn't have a round headlight already, you'll also need fork clamps: OSAN Universal 35mm-43mm Headlight Mount Brackets Fork Ear Motorcycle Chopper Cafe Racer Black https://www.amazon.com/dp/B0171DQ9XA/ref=cm_sw_r_apan_i_8H1NERX1JMR4MGQQNP0J
So, I'm in the middle of trying to make a street/scrambler-style bike out of the DR650. So far, I've got the headlight w/ brackets and a flyscreen from National Cycle. Everything's been bolt-on, no modifications necessary. Cost was about $200, flyscreen cost the most at $140.
You honestly don't even need the flyscreen, I believe the DR has that pouch behind the headlight to hold the electrics (http://www.partzilla.com/parts/search/Suzuki/Motorcycle/2015/DR650SEL5/WIRING+HARNESS+%28DR650SEL5+E03%29/parts.html) #3.
Headlight: https://www.amazon.com/gp/product/B0068C0QJY/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
Bracket: https://www.amazon.com/gp/product/B0171DQ9XA/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
Definitely get the parts that you're missing if you need them (except the wires -- just get new 16 gauge wire, crimping terminals, a plier crimping tool and a wire stripper). On the headlight though, I would hold off. The original headlight housing holds a sealed beam headlight. If you get an Emgo headlight housing or another aftermarket housing, you'll be able to use H4-style bulbs instead.
This is the one that I got, and it's much better quality than the stock housing:
Here's how it looks with an LED bulb:
Working on getting my photos together, btw. I've been procrastinating enough.