Once I realized the part # of an Advance ballast that was H37 and not both H37/M58, I just figured I could go to the corner-store lighting supplier and get them there. (I had assumed that since my H37/M58 combos are Advance, that Advance mustn't make "just H37's"
... not realizing that Advance has about 1000 different models for every ballast designation you can dream of..
) I haven't yet pursued it beyond that.