Hi there,
I can do the job for you. I have extensive expereince developing custom applications similar to this, and working with third party REST API's. Furthermore I have worked with both Shopify Storefront API as well as the Etsy API.
I have gone ahead and placed a bid now and we can get started any time you are ready. I realize my bid is above your posted budget, but unfortunately the posted budget is quite short given the requirements of the project and the work involved.
If you have any questions, please do not hesitate to let me know and I will get back to you asap.
Look forward to hearing from you, and working with you.
Regards,
V