>>1403728there are loads of cheap 25.4mm clamp riser bars on ali and amazon. Just don't get really narrow (sub 600mm) ones.
Your stem is probably 26mm and you can just shim them to fit with strips from a coke can, or get a 25.4 mtb quill.
then just get some new levers and grips and leave your dt/stem shifters as is. most levers come with new cables.