I live in completely different part of the world (Germany), so I don't know whether this will be helpful, but here it is:
Dick Stevens in "Making Kallitypes" gives several ways of making one's own ferric oxalate. I never tried one out from the scratch, but: I am able to obtain ferrous oxalate (I think it is also caled "iron 2 ocxalate"; at least this is, if i remember correctly, the equivalent to the German name) here from a shop selling chemicals and other stuff for school experiments. This seems to be more easily available, and it is an intermediate stage in Stevens' recipy, and quite easy to turn into ferric oxalate with some oxalic acid and hydrogen peroxide. The advantage: you can easily produce the yellow form which is without free oxalic acid, not what you want for pt/pd, but better for kallitypes.
Sodium citrate can be easily produced by adding citric acid to dissolved sodium carbonate in a bucket large enough to contain the fizz, here you want to add a bit more citric after the bubbling stops to get the developer a little bit acidic which helps to clear the prints.