If you look on Adult Incontinence supplies or medical supplies websites. Sometimes they'll have free samples of things.
You could always even ask customer service if they offer free samples.
If you want cheap diapers. Try
https://www.healthykin.com/p-571-attends-care-poly-briefs.aspx Healthykin sells cheap but good disposable adult diapers for $28.95 around $33.00 with shipping for 96 diapers in a case.
I buy these for my mom who's partially incontinent.