I'm looking for an F36T12/HO 2 or 1 lamp ballast. I found some lamps and I want to convert some fixtures to them. It needs to be 120v. I'm hoping someone knows the model numbers of the ballasts?

Here are two Advance YS-2S85-TPs. Each one can power 1 or 2 tubes. Kind of expensive but it is a pack of two ballasts.
https://www.ebay.com/itm/255543314322

 The listing says 120 volts, but the ballast label is red and says 240 volts.

@Ugly1
That is true, I guess I don't know how to read lol

Yes, I had come across that one and didn't buy it for that reason.

Advance RC-2S85-TP is the 120v version of the ballast posted above.

For shorter lamps and for converting existing fixtures the Universal 631-LH-TC-P is probably a better option. The OCV is lower so shorter lamps aren't as likely to instant start and the shorter ballast height means it will fit into more fixtures compared to the Advance.