Nate,you may have trouble finding a trailer in the 12k-14k range,with air brakes.Most trailers in that range have electric brakes.
I think this is in part due to the axles w/air brakes are usually duel wheels,and the weight ratings are 10k/axle and up.
There is electric over hydraulic,and air over hydraulic systems available,but they'll add to the cost of the trailer(over the electric alone).I don't know if the surge brakes are sold anymore,in that weight class.I do still see them on boat trailers,though,so maybe??
The easiest,and least costly would be to fit his truck with an electic brake controller.That would be in the $200-$300 range for that.But if he does not want electric brakes at all,the air over hydraulic may be the best way to match it too his truck,cost wise.
Here are two sites for trailers if price is a concern :
www.kaufmantrailers.com
www.appalachianmfg.com
I don't know if either are quality,or not,but the Kaufman trailer company will motify their spec's for you if needed(I priced a trailer from them,and wanted Oak decking instead of their Pine.They said no prob.!)
I just purchase a 25k trailer made by ABU,but they're in ND.,so the shipping to your area would be alot!!But it seems like a well built trailer.I don't have their web address for you though.Their prices were about $1000-1200 more for the same trailer as Kaufman,but have slightly better spec's(bigger channel,etc.)
I also had found a co. in Oklahoma,called Overbilt trailers.Their trailers were very industrial(and high quality!!)but the prices were higher than I could justify,for my application.You may check them if price isn't a concern,and you want quality.
www.overbilttrailers.com
I'm sure there are alot of other's out there too!!
Good Luck in your search.