I recommend a gaff from origami customs, as they don't charge for making your gaff to custom measurements, and they have a free gaff program.
EDIT: Origami Customs is based out of Canada and they ship internationally. Since I don't see any of their in-person free gaff programs partners in Austria, your best bet will be their online free gaff program through Point of Pride, here are their requirements:
We have only two requirements in an effort to be as inclusive as possible:
You identify as transgender (MTF, genderqueer, non-binary, genderfluid, gender non-conforming, and every other non-cis identity assigned male at birth within the trans umbrella.)
You cannot afford to purchase femme shapewear, or you cannot safely obtain femme shapewear.
We accept all requests for support, and applications are open year-round. Once you complete your application, your request will be added to our waitlist. Shipping is discrete and 100% free, and we ship internationally to 90+ countries and counting.
Point of Pride sources their gaffs from Origami Customs. You have to take measurements, fill out an application on this Google Form, and they will contact you when it's ready to ship. They do ship internationally for free.
I think the main "catch" is that there is a wait-list and presumably a long wait time. Even buying a gaff directly from Origami Customs I placed my order in December 2023 and it didn't ship until March 2024. I suspect it will be a much, much longer wait for a free gaff through Point of Pride.