Can I make Ricotta Impastata?
Ricotta Impestata is apparently ricotta that has been drained and pressed through a fine mesh.  So, while you can order it online, you can also make it yourself by first draining or blotting the ricotta using paper towels or cheesecloth, and then by pressing it through a tight-mesh strainer.  Personally, I would do the draining but not the pressing, as the latter would be a lot of work and probably not make that much of a difference.

Also, having just made proper whey ricotta not 2 hours ago, I suspect that what the "impestata" process duplicates is the texture of fine whey ricotta, which is quite smooth and creamy compared with whole milk ricotta.  So if you make cheese anyway, try making whey ricotta and draining it thouroughly, and that may give you the texture you're looking for.