I found that Czech e-shop has M92 (with cover, electricity supply and 2 year warranty) for cca 320 EUR (incl. VAT) + postage. It should be standard M92 into which it is possible install "Booxstor" firmware.
It is still more exspensive than bare M92 from Arta Tech, but quite close, mainly if you consider aditional cost for cover.
But their pages are in Czech and I do not know if they sell internationaly.
https://www.geekbook.cz/
IVONA is not product of Arta Tech (I think), they licence TTS software from another company called IVONA Software (which is also Polish company).
Amazon buys IVONA Software