Hi @aj20152015
Currently, we don’t have a payment gateway plugin that integrates Sage 200 with WooCommerce. However, you can create your own custom payment gateway plugin using their API.
Please note that writing or providing custom code is not within the scope of our support policy. If you still need help, we recommend asking development questions on the #developers channel of the WooCommerce Community Slack. Many of our developers hang out there and will be able to offer insights into your question. You can also seek help from the following:
I wish I could help more, but hopefully, this gets you going in the right direction to get the job done.