If you like TF-4 when not try mixing TF-2? It's not a rapid fix but other then that it's similar to TF-4. My understanding is TF-4 comes with a high capacity but TF-2 is pretty good and cheap if you mix your own.

250 grams of hypo
15 grams of sodium sulfite
10 grams of sodium metaborate

all for 1litre