Marcin just pointed out that you can use dlopen() in a way that it finds symbols without a library name. That should do, I think.
Note that finding a marginally easier way to do the lookup doesn't address my concern that this undirected search will cause maintenance and porting problems by worsening an already bad situation (just which library did Linux/solaris/freebsd/hpux/redhat6.0/redhat7.0/... choose to hide a symbol in). In fact, I expect that having dlopen do a search through the libraries that it thinks are relevant instead of Hugs performing a search through the list of libraries that it knows to be relevant probably makes things worse because it increases the gap between the programmer's mental model and what actually happens. Alastair ps dlopen is not completely portable - Hugs also uses shl_{load,findsym} (HPUX only?) and {LoadLibrary, GetProcAddress} (Win32).