I did a bibliography search on the object via Simbad and there isn't a lot of data available since the Southworth et al. 2005 article you linked to. Looking at the paper it seems the only other source of photometric data that is mentioned is Kiyokawa and Kitamura, 1975 in Ann. Tokyo Astron. Obs., second series which seems to be a in-house publication of Tokyo Observatory and doesn't seem to be available online. The only recent references are a few times of eclipse, which would help any period change modelling, but not the general modelling of the system.
This situation is not uncommon; there are a lot of binary stars out there and at a period of 2.5 days, this one is quite "expensive" in terms of observing time. This is even more the case if you want to get lightcurves in several filters, to aid the modelling by constraining temperatures etc.