The access to solids is definitely a problem. One approach might be digging them from the surface and lifting up using balloons. High temperatures don't help, but without the need to stay on the surface for very long periods, the digging robots may probably accumulate enough cold while high in the atmosphere, and then dive down for a short while, managing the temperature e.g. by melting and boiling the coolant, then go up again.

The lifting gas can be initially transported in a highly pressurized form (e.g. liquid helium). It would be enough to support a small initial platform. That platform can generate lighter gases right from the atmosphere, using solar energy. CO2 is pretty heavy, so even oxygen and nitrogen would be lifting gases. Hydrogen is also somehow available for extraction from the atmosphere. These gases could be used to support more and more incoming structures as they arrive from orbit. (Yes, easier said than done.)

The bigger problem would probably be compounds like sulfuric acid, hydrogen chloride and fluoride, etc, that would readily react with many construction materials, especially metals.

Given the atmosphere composition, it's probably even possible to synthesize both fuel and oxidizer for a rocket, e.g. hydrocarbons and O2 or HNO3. Launching a large rocket from a zeppelin is tricky. Launching a rocket from a plane has been shown to work on Earth, so it's possibly also doable from Venusian cloud tops. Again, easier said than done.

But still possible!