Yes Tulcea LRTC has AVGAS, also Suceava LRSV has some at our private club (my site, please with prior arrangement), Constanta LRCK hasn't but Tulcea LRTC is not far and in the way from Suceava LRSV and somehow from Arad LRAR. I don't know about gas at Arad, LRAR, I'll investigate.
Indeed Arad LRAR is international so OK for entry, as is Constanta LRCK for exit to Istanbul.
Some activity at Suceava LRSV.