Is there a way to pull data from the GSA website to calculate per diem rates in custom fields on a custom object?

I would like to essentially replicate the fields from the GSA website where users would enter their dates of travel and location and have the per diem rates (including M&IE) automatically populated. I am not interested in a big package with a bunch of other services, but I wanted to see if there was already an integration or an app that others have used before I try to make this from scratch or find other less-preferred options. If someone has already done something like this, guidance on how you executed it would also be appreciated. Thank you!