How to call MS Graph via sp_invoke_external_rest_endpoint with a large access token?

I'm using sp_invoke_external_rest_endpoint in T-SQL to call Microsoft Graph endpoints. This is one of the use cases that Microsoft advertises. The headers parameter of sp_invoke_external_rest_endpoint is an nvarchar(4000) so you are limited to 4000 characters. How do you call MS Graph when you have an access token that is larger than that?

I've implemented sp_invoke_external_rest_endpoint in two different environments and in one of them the access token was short enough (around 3400 characters) to fit but in the other it's over 4000 characters.