Which handlebars should I use flats or drops?
Try a pair of bullhorn bars and see how you get on. If they cure your problem, then it’s job done at much less cost than
a new bike. If not, then you should find converting to a dropped handlebar more
cost-effective than buying a new bike.
Without knowing the existing spec it is hard to give specifics, but the major expenses are likely to be the handlebar, brake levers, and shifters. Down-tube or bar-end shifters make inexpensive alternatives to dual-control levers, while low-cost drop-bar brake levers are available for linear pull, cantilever, sidepull, and mechanical disc brakes.
Cycle’s Technical Editor