1200y3: Uhm, what do you need an app for? You just need to remember the formula for parallel resistance, which is 1/R(total) = 1/R(1) + 1/R(2) (+ 1R(3) et cetera...), and apply it accordingly. So you get 1 / (1/33 kOhm - 1/47 kOhm) = ca. 111 kOhm. Closest usual, easily available value should be 110 kOhm.
Disadvantage of the usual, external approach via Y-splitters and loading plugs would be an at least slight increase in cabling capacity, though. However, if one would like to avoid that, and provided there's sufficient space inside the plug shells, one can just as well integrate the resistors in the output cable plugs of the turntable.
Werner: Sorry, there used to be a schematic from some DIY-oriented audio forum one could easily find via Google's picture search, but that seems to have disappeared in the meantime. If you could provide a reasonably highly resolved pic of both sides of the PCB, it shouldn't be all to difficult to identify the responsible resistors, though - provided you'd really prefer an internal modification. Alternatively you could try to contact fellow VE user Werner (from Belgium), 'cause iirc he had provided that schematic. So maybe he can repost it here or at least send it to you...
Greetings from Munich!
Manfred / lini