Yeah, but they tend to be lower efficiency (UEF 3.0) and CA rebate program requires UEF 3.3 or higher, which apparently you can only get by switching to the higher voltage.
Edit: to clarify, I was referring to the California state rebate of $700 or $900 (depending on capacity) taken off the purchase price at checkout. The federal tax credit of 30% applies to the 120V drop-in replacement as well as the 240V models.
I checked Home Depot today and, oddly, all the Rheem 240V models are selling for less than the 120V models of the same capacity, even before rebates.
If I do get a 240V model, I certainly would just disable the resistance heating mode, which all the Rheem models (and probably all models, period) have the option to do.