What models are you using? Your problem seems simpler than general NER (just identifying a subset of entities). I would wager a good ol' LSTM or GRU can do it just fine.
We have trained our custom NER to detect merchants using millions of transactions as training data rather than a general NER.
We have tested with a few general NER models but they weren't detecting merchants properly. We haven't tested with LSTM/GRU yet but that's a good suggestion!