Best bet would be to phone the club using the number on the info page during office hours. Someone would be able to give you an answer. There's no where you can buy shirts online but they might do mail order, I don't know these days.
On a side note, I would recommend Westleigh Park as a place to help with the agoraphobia. Ive suffered with similar problames myself and I started coming as a way to get out more and its helped me a lot
The lessons learnt from the FA Cup run still live on... Westleigh Park has better paper towel dispensers than Anfield!!