If you want more common and easier to use unlimited bombs than No 2, and don't mind a hard challenge, the Blue Bomber challenge unlocks Gold Bombs, which are unlimited bombs for one floor. And they're pretty common, you'll generally see one or two of them every run.
But Blue Bomber is kind of a rough challenge.
There's a new item on the PC version that makes Gold Bombs kind of hilarious to use since it removes the bomb drop speed cap. I think that item is coming to the Switch... eventually
Nice, sounds like something worth trying.