He cannot wear ihram because he is disabled

Yes, if a person cannot wear the ihram garments, he may wear whatever suits him of other permissible types of clothing. And according to the scholars he has to either sacrifice a sheep and distribute its meat to the poor; or feed six poor persons, giving each one half a saa‘; or fast three days. 

This is what the scholars said, drawing an analogy with what is said about shaving the head, as Allah, may He be exalted, said (interpretation of the meaning):

“and do not shave your heads until the Hady reaches the place of sacrifice. And whosoever of you is ill or has an ailment in his scalp (necessitating shaving), he must pay a Fidyah (ransom) of either observing Saum (fasts) (three days) or giving Sadaqah (charity – feeding six poor persons) or offering sacrifice (one sheep)”

[al-Baqarah 2:196]. 

The Prophet (blessings and peace of Allah be upon him) explained that fasting here means three days, giving charity means feeding six poor persons, giving each one half a saa‘, and offering a sacrifice means slaughtering a sheep. Slaughtering of the sheep and feeding the poor in this case should be done in Makkah to be on the safe side, because the transgression of wearing ordinary clothes will continue until one exits ihram. End quote. 

Majmoo‘ Fataawa Ibn ‘Uthaymeen, 22/138