It will be helpful to list the specific payment method you need, to help potential developers understand if the project is a good fit for their skills. We've done lots of payment modules for multiple eCommerce carts over the years and the payment method requirements, quality of payment gateway API documentation and vendor support vary greatly, etc.
Regardless of who you choose to implement your payment method addon, please do be careful to hire someone who is knowledgeable and skilled enough to deliver a secure solution that will meet Payment Card Industry (PCI) guidelines. There is virtually no other part of your eCommerce store that is as critical to have built securely as the software that handles your customer's credit card information. Companies that are qualified to do this aren't cheap, and they aren't "fast". There's a lot of QA and security testing that goes into delivering a properly coded payment module, even if the API happens to be one of the easier ones to integrate with. And that's even more important for the more challenging APIs.
~ Deb Cinkus, CEO
Polished Geek: more with monday․com
eCommerce Business Process Automation Experts
