I love my drop bar MTB. It can take a bit of money and work to get one going, though. Really have to work to make 'em fit also. Getting an appropriate reach requires going down a size or two. Can be tough if you need an ETT of 54cm or less.

I'd look for rigid mid-90s rigs of 25 lbs or less.

Barracuda A2m (25.5 but tire change brings it to 25.0), Parkpre Pro 825 (a lot of years/versions are listed at 23.5lbs!!!), 1996 Mongoose IBOC Zero-G, several years of the KHS Comp, or Montana Comp, etc. Some Montana Team and Pro non-suspensions also.

I'm a steel fan so those are all steel, plenty of aluminum choices also. I'd probably peruse mid-90s bikepedia listings, most manu's listed weights back then so you can make a list of light ones to keep an eye out for.

I did my first drop bar conversion with barend shifters I got for $20, bars for $10, stem for $10, FD for $10. Then got these Ultegra 9-speed brifters for $45...



I tended to spin out a bit with the 44T big ring when running 1.4" slicks so went with a road double right crank eventually. Shown with 1.75" tires here, but gearing's nice for road with those tires too.