Hi Rugo,
Welcome to IIS.
Your question is a difficult one. Not many manufacturers have the capacity to provide full blown
interferometer statistics on their mirrors. Such a process can be costly and time consuming. There are mirror manufacturers that still provide this information on request (usually, they send the mirror to a tester). The mirror purchaser pays the cost for this to be performed unless negotiated otherwise.
In the US, manufacturers such as
Star Instruments will always provide mirror quality documents from their interferometer. There are a few others that will do the same. Depends on what you are willing to pay. Shop around.