external equiv to R_serialize()?

I'm trying to efficiently allow conversion of R objects to PostgreSQL 
bytea (raw binary) datatype within PL/R for persistent storage in 
Postgres tables. I have found R_serialize() which looks like what I 
need, -- e.g. R_serialize(object, NULL, FALSE, NULL) -- except that it 
is marked attribute_hidden. Is there some other externally available 
interface that I can use?

Thanks,

Joe