The smaller sized cartridges are a bit easier to find. If you are willing to compromise brew quantity for a cheaper product with more readily accessible cartridges you could get one of these and use the N2 2-gram cartridges.
I have this one, comes with metal and plastic screw in
I'm talking something like this. We just call them crackers. Like I said I use them any time I've done nitrous without issue.
He's not talking about a cracker. He is talking about one of these:
https://www.amazon.com/Professional-Whipped-Cream-Dispenser-Decorating/dp/B089QT6LG6
Which you absolutely can inhale directly from.