Unobtainable (adjective)
Unable to be obtained: not able to be acquired or reached.
Unobtainable (noun)
Someone or something that cannot be obtained.
Unattainable (adjective)
Impossible to attain or reach; unable to accomplish
“inaccessible|unobtainable|unapproachable”
Unattainable (noun)
Anything that cannot be attained.
Wiktionary
Unobtainable (adjective)
not able to be obtained
“the book was unobtainable in London so I wrote to the publisher”
Unattainable (adjective)
not able to be reached or achieved
“an unattainable goal”
Oxford Dictionary