I have a Canon EF-S 60mm Macro lens.
Can I add an extension tube or teleconverter to emulate a 100mm Macro?
If not, is there a solution?
No, an extension tube doesn't really increase the focal length of your lens, it just allows it to focus on closer subjects.
Assuming you want to shoot subjects farther away than with the 60mm, to turn your 60mm into a 100m, you would need either:
The real question is whether the resulting definition of your pictures is still the same. If you get a 2px blur/softness, you are better off cropping the picture from the plain 60mm.
The non-IS Canon 100mm is easily found on the second-hand market. Tamron and Sigma also have very good macro lenses in the 90-110mm range