I have used the i-Tasser several times, however it has been unavailable for several days. I tried the swiss-model, but the output was not very pleasant due to the model used. Is there any other server that I can use?
Swiss-Model, Phyre2 or ModWeb work fine if your query protein has enough high homology to one or more templates in PDB. I-Tasser helps to identify more distantly related proteins (with similar fold). Raptor-X can also be helpful.
However, the most important questions here are "Are there any known templates for my query protein?" (and how good are they?), "How reliably can the region of interest be modeled?", etc.