Hi @momo-fr,
You’re right, there is currently no wrapper for file inputs. This is because the official Material Components Web also does not yet have file inputs implemented.
It is on my to-do list to build one myself but I have no ETA on that.
Unfortunately that means whatever you use for file upload will look different to the rest of the form. One option you have though is to embrace that and use something like Drop Uploader for CF7 for a totally different style for your file field (different enough that it won’t clash).
Sorry, that’s the best alternative at the moment.