Just put a roof rack on my 3rd Gen. There is a 1.5in - 1.75in gap between the rack and the body on the front, I can adjust the distance slightly. It looks fine, but I thought it would look really good if I could fill that gap with a slim light bar. I don't like the look of the large light bar on top. Just curious if you all had any suggestions, I'm having trouble finding any good options, looking to keep the price on the lower end. Picture of exactly what I'm talking about is linked below.
Thanks in advance!
Light Bar Gap - Album on Imgur

Are you looking to fill the whole gap? If so, you're never gonna find a ~40in bar on the "lower end," even crap ones are pricey. $200-300 is a pretty average price and it's also highly dependent on how many lumens, beam pattern, wattage, etc. That said, it would look really good going the whole length of the gap.
In regards to the width, most single row bars are roughly 1.5" tall, but needless to say most websites will give you the specs anyways. When I was looking for a bar to put behind my scoop, I just googled "10 inch LED bar" or something similar and would browse until spotting one I liked, looked at the specs, debated price, and kept going until something fit my search; basic window shopping.
extremeledlightbars.com is a sponsor of t4r if you haven't checked them out. Not too expensive and look pretty good.

Night rider leds makes single row in about any length. Price falls between rigid and Chinese. Quality looks decent and some are even DOT approved.

Did you mention the actual width of the bar you ended up using somewhere? I'd be interested what you used.

I didn't realize 10" would fit.

don't say it...don't say it...."that's what she said" -sorry couldn't help it.

Yep, I used a C3 bar from Raxiom. 10.84-inch Wide X 1.53-inch Height X 1.87-inch Deep. The C3 bar in particular works great as a fog/aux light, subpar for a spot/flood beam, fwiw.