Custom component file locations in Qsys

Managed to find a solution. By creating a .ipx file (which must be in the same folder as the .sopc file) you can provide project local IP. The Quartus Handbook recommends using ip-make-ipx to build an ,ipx file that actually lists the components so that Qsys doesn't have to search them out on a simple .ipx file with a <path> directive. But Qsys already has to search so much IP from the Altera provided stuff that having to scan the local stuff too is a pretty minor additional time hit.