Here is a list of payment gateways that you can add to your checkout to take payments.
Afterpay
Click by Paymark
DPS/Windcave
Laybuy
Ninja Pay (Via Fat Zebra)
PayPal
Stripe
ZipPay
Please contact support for the implementation cost. You can email support@webninja.com.au or create a ticket here https://webninja-support.zendesk.com/hc/en-us/requests/new